The 'Battle of the Netherlands' was the German invasion and conquest of the Netherlands within the 'Gelb' undertaking to defeat the Netherlands, Belgium, Luxembourg and France (10/17 May 1940).

The battle lasted from 10 May until the surrender of the main Dutch forces on 14 May, but Dutch troops in the province of Zealand continued to resist until 17 May, the date on which the Germans completed their occupation of the whole country.

The invasion of the Netherlands saw some of the earliest large airborne operations, which were made for the occupation of tactical points and thus to assist the advance of the ground forces. The Luftwaffe used paratroopers in the capture of several airfields in the areas of Rotterdam and The Hague, thereby helping the rapid overrunning of the country and the immobilisation of Dutch forces.

After the devastating Luftwaffe bombing of Rotterdam on 14 May, the Germans threatened to bomb other Dutch cities unless the Dutch forces surrendered. The last German-occupied parts of the Netherlands were liberated only in 1945.

The UK and France declared war on Germany in September 1939 after the German 'Weiss' (i) invasion of Poland, but no major land operations occurred in Western Europe during the period known as the Phoney War in the winter of 1939/40. During this time, the British and French built up their forces in expectation of a long war, and the Germans together with the Soviets completed their seizure of Poland. On 9 October, Adolf Hitler ordered the planning of an invasion of the Low Countries as a base for use against the UK and to pre-empt a similar attack by the Allied forces, which could threaten the vital Ruhr industrial region of north-western Germany. A joint Dutch and Belgian peace offer between the two sides was rejected on 7 November.

The Dutch were poorly prepared to resist such an invasion. When Hitler came to power, the Dutch had begun to re-arm, but more slowly than France or Belgium: only in 1936 did the Dutch defence budget start a gradual increase. Successive Dutch governments avoided the open identification of Germany as an acute military threat. This was the result in part of a wish not to antagonise a vital trade partner, even to the point of repressing criticism of Nazi policies, and also in part of the inevitability of the Dutch policy of strict budgetary limits with which the conservative Dutch governments had sought, without success, to fight the 'Great Depression' that had hit the Dutch particularly hard. Hendrikus Colijn, the prime minister between 1933 and 1939, was personally convinced that Germany would not violate Dutch neutrality, and senior officers made no effort to mobilise public opinion in favour of improving the nation’s military defence.

International tensions increased steadily in the late 1930s. Crises were caused by the German occupation of the Rhineland in 1936; the Anschluss (annexation) of Austria and the Sudeten borderland crisis of Czechoslovakia in 1938; and the German occupation of Bohemia and Moravia and the Italian invasion of Albania in the spring of 1939. These and other events forced the Dutch government finally to consider the world situation with less blinkered eyes, but the government nonetheless limited its reaction as much as it could. The most important measure was a partial mobilisation of 100,000 men in April 1939.

After the German invasion of Poland in September 1939 and the ensuing outbreak of World War II, the Netherlands hoped to remain neutral, as they had done during World War I 25 years earlier. To ensure this neutrality, the Dutch army was mobilised from 24 August and readied defensive undertakings. Large financial sums were spent on defence. It proved very difficult to obtain new matériel in wartime, however, especially as the Dutch had ordered some of their new equipment from Germany, which deliberately delayed deliveries. Moreover, a considerable part of the funds were intended for the defence of the Netherlands East Indies, including the construction of three battle-cruisers.

The strategic position of the Low Countries, sandwiched between France and Germany on the uncovered flanks of their fortification lines, made the area a logical route for an offensive by either side. In a radio speech on 20 January 1940, Winston Churchill, the First Lord of the Admiralty, tried to convince the Dutch not to wait passively for an inevitable German attack, but to join the Anglo-French Entente. Both the Belgians and the Dutch refused, even though the German attack plans had fallen into Belgian hands after a German aeroplane crash in January 1940, in what became known as the Mechelen Incident.

The French supreme command considered the violation of the Low Countries' neutrality if they had not joined the Anglo-French coalition before the large Allied offensive being planned for implementation in the summer of 1941, but the French cabinet, fearing a negative public reaction, vetoed the idea. Kept in consideration was a plan to invade should Germany attack the Netherlands alone, necessitating an Allied advance through Belgium, or if the Netherlands assisted the Germans by tolerating the latter’s advance into Belgium through the southern part of their territory: both possibilities were discussed as part of the hypothèse Hollande. The Dutch government never officially formulated a policy on how to act in case of either contingency: most ministers preferred to resist an attack, and a minority of the ministers as well as Queen Wilhelmina refused to become a German ally whatever the circumstances. The Dutch tried on several occasions to act as an intermediary to reach a negotiated peace settlement between the Allies and Germany.

After the German 'Weserübung' invasion of Norway and Denmark on 9 April 1940, followed by a warning by the new Japanese naval attaché, Captain Tadashi Maeda, that a German attack on the Netherlands was certain, it became clear to the Dutch military that staying out of the conflict might prove impossible. The Dutch high command began a full preparation for war, both mentally and physically. Dutch border troops were put on greater alert. Reports of the presumed actions of a 'fifth column' in Scandinavia caused widespread fears that the Netherlands too had been infiltrated by German agents assisted by traitors. Countermeasures were taken against a possible assault on airfields and ports.

On 19 April a state of emergency was declared, but most civilians still cherished the illusion that their country might be spared. The Dutch hoped that the restrained policy of the Entente and Central Powers during World War I might be repeated, and therefore sought to avoid the attention of the 'great powers' and a war in which they feared a loss of human life comparable to that of the previous conflict. On 10 April the UK and France repeated their request that the Dutch enter the war on their side, but were again refused.

Within the Netherlands, all the objective conditions were present for a successful defence: a dense population that was wealthy, young, disciplined and well-educated; a geography favouring the defender; and a strong technological and industrial base including an armaments industry. However, these had not been exploited usefully: while the German forces of the time still had many shortcomings in equipment and training, the Dutch army, by comparison, was far less well prepared. The myth of the German general equipment advantage over the opposing armies in the Battle of France was in fact a reality in the case of the 'Battle of the Netherlands'. Germany had modern forces with tanks and dive-bombers, while the Netherlands had an army whose armoured forces comprised only 39 armoured cars and five tankettes, and an air force consisting largely of biplanes. The Dutch government’s attitude towards war was reflected in the state of the country’s armed forces, which had not significantly expanded their equipment since before World War I, and were inadequately armed even by the standards of 1918. During the 1920s, an economic recession lasting from 1920 to 1927 and the general détente in international relations had led to a limitation of the defence budget. In both 1931 and 1933, commissions appointed to economise even further failed, because they concluded that the acceptable minimum had been reached and advised that a spending increase was urgently needed. Only in February 1936 was a bill passed creating a special defence fund.

The lack of a trained manpower base, a large professional organisation, or sufficient matériel reserves precluded any swift expansion of the Dutch forces. There was only just enough artillery to equip the larger formations and units: eight infantry divisions combined in four corps, one light (i.e. motorised) division and two independent brigades (Brigade A and Brigade B), each with the strength of half a division or five battalions. All other infantry combat units were raised as light infantry battalions that were dispersed all over the country to delay enemy movement. About 2,000 pillboxes had been constructed, but in lines without any tactically significant depth. There were no large modern fortresses such as the Belgian stronghold of Eben Emael, and the only modern fortification complex was that at Kornwerderzand, guarding the Afsluitdijk. The Dutch forces equalled 48 infantry regiments as well as 22 infantry battalions for strategic border defence. In comparison, despite its smaller and more aged male population, Belgium fielded 22 full divisions and the equivalent of 30 divisions when smaller units were included.

After September 1939, desperate efforts were made to improve the situation, but with very little in the way of positive results. For obvious reasons, Germany delayed the delivery of ordered equipment for the equipment of an army that would not unequivocally take its side. The one abundant source of readily available weaponry was the USSR, but was inaccessible because the Dutch, contrary to most other nations, did not recognise the communist régime. An attempt in 1940 to procure Soviet armour captured by Finland failed.

On 10 May, the most conspicuous deficiency of the Dutch army was its shortage of armour. Whereas the other major combatants each possessed a considerable armoured force, the Netherlands had not been able to obtain the minimum of 146 modern tanks (110 light and 36 medium) it had already considered necessary in 1937. A single Renault FT light tank, for which just one driver had been trained and which had the sole task of testing anti-tank obstacles, had remained the only example of its kind and was no longer in service by 1940. There were two squadrons of armoured cars, each with a dozen Landsverk M36 or M38 vehicles. Another dozen DAF M39 cars were in the process of being taken into service, some still having to be fitted with their main armament. A single platoon of five Carden-Loyd Mark VI tankettes used by the artillery completed the list of Dutch armour.

The Dutch artillery had available a total of 676 field guns and howitzers: 310 Krupp 75-mm (2.95-in) field guns, partly produced under licence; 52 105-mm (4.13-in) Bofors howitzers, the only really modern pieces; 144 obsolete Krupp 125-mm (4.92-in) guns; 40 150-mm (5.91-in) sFH13 howitzers; 72 Krupp 150-mm (5.91-in) L/24 howitzers; and 28 Vickers 152-mm (5.98-in) L/15 howitzers. In the anti-tank role, 386 Böhler 47-mm L/39 weapons were available: these were effective weapons but too few in number, being only at a third of the planned strength; another 300 antiquated 6 Veld 57-mm and 8 cm staal (84-mm/3.31-in) field guns performed the same role for the covering forces. Only eight of the 120 modern 105-mm (4.13-in) pieces ordered from Germany had been delivered at the time of the invasion. Most artillery was horse- rather than truck/tractor-drawn.

The Dutch infantry used about 2,200 7.92-mm (0.312-in) Schwarzlose M.08 machine guns, partly manufactured under licence, and 800 Vickers machine guns. Many of these were installed in the pillboxes. Each infantry battalion had one company of 12 a heavy machine guns. Dutch infantry squads each included one light machine gun, the Lewis M.20 weapon, of which about 8,000 were available. Most Dutch infantrymen were equipped with the Geweer M.95 rifle, which had been adopted in 1895. There were only six 80-mm (3.15-in) mortars for each regiment. This lack of firepower seriously impaired the Dutch infantry’s fighting capability.

Despite the fact that the Netherlands was the home of Philips, one of Europe’s largest producers of radio equipment, the Dutch army relied to a large extent on telephone connections, and only the artillery had been equipped with the modest number of 225 radio sets.

On 10 May, the Dutch air force, which was part of the army rather than an independent arm of the Dutch armed forces, had a fleet of 155 aircraft: 28 Fokker G.I twin-engined 'destroyer' (heavy fighter) machines; 31 Fokker D.XXI and seven Fokker D.XVII fighters; 10 twin-engined Fokker T.V, 15 single-engined Fokker C.X and 35 single-engined Fokker C.V light bombers, 12 Douglas DB-8 dive-bombers used as fighters and 17 Koolhoven FK-51 reconnaissance aircraft. Some 74 of these 155 aircraft were biplanes, and of the total 125 were operational. Of the remainder, the air force school used three D.XXI, six D.XVII, one G.I, one T.V and seven C.V aircraft, along with several dedicated training aeroplanes. Another 40 operational aircraft served with the Marineluchtvaartdienst (naval air service) along with about an equal number of reserve and training craft. The production potential of the Dutch military aircraft industry, consisting of the Fokker and Koolhoven, companies was not fully exploited as a result of budgetary constraints.

The Dutch army was thus poorly equipped, and it was also poorly trained. Little experience had been gained in the handling of units larger than the battalion. From 1932 to 1936, the Dutch army undertook no summer field manoeuvres in order to conserve military funding. Also, the individual soldier lacked many necessary skills. Before the war only a minority of young men eligible to serve in the military had actually been conscripted. Until 1938, those who were enlisted served for only 24 weeks, just enough to receive basic infantry training. In that same year, service time was increased to 11 months. The low quality of the conscripts was in no way offset by any large body of professional military personnel: in 1940, there were only 1,206 professional officers. It had been hoped that when war threatened, these deficiencies could be remedied quickly, but following the mobilisation of all the Dutch forces on 28 August 1939, bringing the army’s strength to about 280,000 men, readiness improved only slowly: most available time was spent constructing defences. During this period, munition shortages limited live-fire training, while unit cohesion remained low. By its own standards, the Dutch army in May 1940 was unfit for battle. It was incapable of undertaking an offensive, even at divisional level, while the execution of manoeuvre warfare was far beyond its capacities.

Together with Hitler, German generals and tacticians had a low opinion of the Dutch military and expected that the core region of Holland proper could be conquered in about three to five days.

In the 17^th century, the Dutch Republic had devised a defensive system called the Oude Hollandsche Waterlinie (Old Hollandic Water Line), which during the Franco-Dutch War (1672/78) protected all major cities in the west by flooding part of the countryside. In the early 19^th century this line was shifted somewhat to the east, beyond Utrecht, and later modernised with fortresses. This new position was called the Nieuwe Hollandsche Waterlinie (New Hollandic Water Line). The line was reinforced with new pillboxes in 1940 as its fortifications were perceived as being obsolete. The line was located at the extreme eastern edge of the area lying below sea level, which allowed the ground in front of the fortifications to be inundated easily with a few feet of water, too shallow for boats, but deep enough to turn the soil into an impassable quagmire. The area to the west of the New Hollandic Water Line was called Vesting Holland (Fortress Holland), whose eastern flank was also covered by the IJsselmeer and the southern flank protected by the lower course of three broad parallel rivers: the Maas and two branches of the Rhine. The Vesting Holland functioned as a 'national redoubt', and was expected to hold out for an extended period of time (in the most optimistic predictions as much as three months without any Allied assistance) even though the size of the attacking German force was strongly overestimated. Before the war the Dutch intention was to fall back to this position almost immediately, after a concentration phase in the Gelderse Vallei, inspired by the hope that Germany would only travel through the southern provinces on its way to Belgium and leave Holland proper untouched. In 1939 it was understood that such an attitude posed an invitation to invade and made it impossible to negotiate with the Allies about a common defence. Proposals by German diplomats that the Dutch government would secretly assent to an advance into the country were rejected.

From September 1939 a more easterly main defence line was constructed. This second main defensive position had a northern part formed by the Grebbelinie (Grebbe line), located at the foothills of the Utrechtse Heuvelrug, an ice-age moraine between the IJsselmeer and the Nederrijn river. It was dug at the instigation of the field army’s commander, Luitenant-generaal Jan Joseph Godfried Baron van Voorst tot Voorst. This line was extended by a southern part, the Peel-Raamstelling (Peel-Raam Position), located between the Maas river and the Belgian border along the Peel marshes and the Raam river, as ordered by the Dutch commander-in-chief, Generaal Izaak H. Reijnders. In the south the intention was to delay the Germans as much as possible to cover a French advance. The Dutch IV Corps and II Corps were positioned at the Grebbelinie; the III Corps was stationed at the Peel-Raamstelling with the Light Division behind it to cover its southern flank. Brigade A and Brigade B were positioned between the Nederrijn and Maas rivers. The I Corps was the strategic reserve in the Vesting Holland, whose southern perimeter was held by another 10 battalions and eastern perimeter by six battalions. All these lines were reinforced with pillboxes.

In front of this main defence line was the IJssel-Maaslinie, a covering line along the IJssel and Maas rivers, connected by positions in the Betuwe, again with pillboxes and lightly occupied by a screen of 14 'border battalions'. Late in 1939, Van Voorst tot Voorst, reviving plans he had developed in 1937, proposed to make use of the excellent defensive opportunities these rivers offered. He suggested a shift to a more mobile strategy by fighting a delaying battle at the plausible crossing sites near Arnhem and Gennep in order to force the German divisions to spend much of their offensive power before they had reached the main defence line, and ideally even defeat them. This was deemed too risky by the Dutch government and Reijnders. The latter wanted the army first to offer heavy resistance at the Grebbelinie and Peel-Raamstelling, and then to fall back to the Vesting Holland'. This also was considered too dangerous by the government, especially in light of German air supremacy, and had the disadvantage of having to undertake the full preparation of two lines. Reijnders had already been denied full military authority in the defence zones, and the dispute about strategy further undermined his political position. On 5 February 1940 Reijnders was forced to offer his resignation because of these disagreements with his superiors, and was replaced by Generaal Henry G. Winkelman, who decided that in the north the Grebbelinie would be the main defence line on which the decisive battle was to be waged, partly because it would there be easier to break out with a counter-offensive if the conditions were favourable. However, he took no comparable decision regarding the Peel-Raamstelling.

During the 'Phoney War', the Netherlands officially adhered to a policy of strict neutrality. In secret, however, the Dutch military command, acting in part on its own accord, negotiated with both Belgium and France, via the Dutch military attaché in Paris, Luitenant-kolonel David van Voorst Evekink, to co-ordinate a common defence to a German invasion. This attempt failed as a result of the insurmountable differences of opinion about the question of which strategy to follow.

Given its obvious strategic importance, Belgium, though in principle neutral, had already made quite detailed arrangements for co-ordination with Allied forces. This made it difficult for the Dutch to have these plans changed to accommodate their wishes. The Dutch desired the Belgians to connect their defences to the Peel-Raamstelling, which Reijnders refused to abandon without a fight. He did not approve of a plan by Van Voorst tot Voorst to occupy a so-called 'Oranje Positie' (Orange Position) on the much shorter line between 's-Hertogenbosch and Tilburg in order to form a continuous front with the Belgian lines near Turnhout as proposed by Belgian General Raoul van Overstraeten.

When he assumed command, Winkelman intensified the negotiations, proposing on 21 February that Belgium man a connecting line with the Peel-Raamstelling along the Belgian part of the Zuid-Willemsvaart. The Belgians refused to do this unless the Dutch reinforced their presence in Limburg, but the Dutch had no forces available with which to fulfil this requirement. Repeated Belgian requests to reconsider the 'Oranje Positie' were refused by Winkelman, so the Belgians decided to withdraw, in the event of an invasion, all their troops to their main defence line, the Albert Canal. This created a dangerous gap, some 25 miles (40 km) wide, and the French were invited to fill this. The French commander-in-chief, Général d’Armée Maurice Gamelin, was more than interested in including the Dutch in his continuous front as he hoped to circle around the German 'Westwall' defences when the Allies launched theirs planned 1941 offensive. Gamelin did not dare to stretch his supply lines that far,however, unless the Belgians and Dutch took the Allied side before the German attack. When both nations refused, Gamelin made it clear that his French forces would occupy a connecting position near Breda. The Dutch did not fortify this area. In secret, Winkelman decided on 30 March immediately to abandon the Peel-Raamstelling at the start of a German attack and withdraw his III Corps to the Linge to cover the southern flank of the Grebbelinie, leaving only a covering force. This Waal-Lingestelling was to be reinforced with pillboxes, for whose construction the military budget was to be specially increased.

After the German attack on Denmark and Norway in April 1940, when the Germans first made use of major airborne forces, the Dutch command became concerned about the possibility that the Netherlands too could become the victim of a strategic assault of this nature. To repulse any such attack, five infantry battalions were positioned at the main ports and air bases, such as The Hague airfield of Ypenburg and the Rotterdam airfield of Waalhaven. These were reinforced by additional anti-aircraft guns, two tankettes and 12 of the 24 serviceable armoured cars. These specific measures were accompanied by more general ones: the Dutch had posted no less than 32 hospital ships throughout the country and 15 trains to facilitate troop movements.

In addition to the Dutch army and General Georg von Küchler’s German 18^th Army, a third force, not significantly smaller than either the Dutch or the German armies, would operate on Dutch soil. This was Général d’Armée Henri Giraud’s French 7ème Armée, which possessed its own particular objectives within the larger French strategy: French strategic planning had long considered the possibility of operations in Dutch territory. The coastal regions of Zealand and Holland were difficult to negotiate because of their many waterways, but both the French and the Germans saw the possibility of a surprise flanking attack in this region. For the Germans this would have the advantage of bypassing the Antwerp-Namur line. The Zealand islands group was seen as strategically critical, as they are just opposite the Thames river estuary, so its seizure would pose a special menace to the safety of England.

Rapid forces, for offensive or defensive purpose, were needed to deny vital locations to the Germans. Long before the Germans, the French had contemplated the use of airborne forces to achieve speedy attacks. As early as 1936 the French had commissioned the design of light airborne tanks, but these plans had been abandoned in 1940, as the French possessed no transport aircraft large enough to carry them. A naval division and an infantry division were earmarked to depart for Zealand to block the western arm of the Scheldt river against a German crossing. These would send forward forces over the Scheldt river estuary into the islands, supplied by sea.

Gamelin feared that the Dutch would be tempted into a quick capitulation or even an acceptance of German 'protection'. He therefore reassigned the former French strategic reserve, the 7ème Armée, to operate in front of Antwerp to cover the river’s eastern approaches in order to maintain a connection with the Vesting Holland farther to the north and preserve an Allied left flank beyond the Rhine river. The force assigned to this task consisted of the XVI Corps d’Armée, comprising the 9ème Division Motorisée, which also included some tracked armoured vehicles, and the 4ème Division d’Infanterie; and the I Corps d’Armée, comprising the 25ème Division Motorisée and the 21ème Division d’Infanterie. This army was later reinforced by the 1ère Division Légère Mécanisée, an armoured division of the French cavalry and a first-class formation. Together with the two divisions in Zealand, seven French divisions were dedicated to the operation.

Although the French troops would have a higher proportion of motorised units than their German adversaries, in view of the respective distances to be covered, they could not hope to reach their assigned sector advancing in battle deployment before the Germans. The French force’s only prospect of beating the Germans to both sides' objective lay in the use of railway transport. This implied that the force would be vulnerable in its concentration phase as it assembled near Breda. The French needed the Dutch troops in the Peel-Raamstelling to delay the Germans for a few extra days to allow a French deployment and entrenchment, but French rapid forces would also provide a security screen. This comprised the reconnaissance units of the armoured and motorised divisions, equipped with the relatively well-armed Panhard 178 armoured car. The vehicles were to be concentrated into two task forces named after their commanders as the Groupe 'Beauchesne' and Groupe 'Lestoquoi'.

During the many changes in the development of the German operational plans for 'Gelb', the idea of ignoring the Vesting Holland, just as the Dutch hoped, was at times considered. The plan’s first version, of 19 October 1939, suggested the possibility of a full occupation if conditions were favourable. In the version of 29 October it was proposed to limit the German violation of Dutch neutrality to a line to the south of Venlo. In the Holland-Weisung (Holland Directive) of 15 November it was decided to conquer the entire south of the country, but in the north to advance no further than the Grebbelinie, and to occupy the Frisian islands group. Generalfeldmarschall Hermann Göring insisted on a full conquest as his Luftwaffe needed the Dutch airfields to operate against the UK, and was also concerned lest the Allies reinforce the Vesting Holland after a partial defeat and use its airfields to bomb German cities and troops. Another rationale for the conquest of the whole of the Netherlands was that, as the fall of France itself could hardly be taken for granted, it was for political reasons seen as desirable to obtain a Dutch capitulation, because a defeat might well bring less hostile governments to power in the UK and France. A swift defeat would also free troops for redeployment to other sectors.

Although it was thus on 17 January 1940 that the decision was made to conquer the whole of the Netherlands, few formations and units could be made available for this task. The main effort of 'Gelb' was to be made in the centre as 'Sichelschnitt', between Namur and Sedan in France. The attack on central Belgium was only a feint, and the attack on the Vesting Holland only a subsidiary of this feint. Although both Generaloberst Walter von Reichenau’s 6^th Army and von Küchler’s 18^th Army were deployed on the Dutch border: the first, and considerably larger, force was to attack south of Venlo to Belgium, leaving just the second to defeat the Dutch main strength. Of all German armies to take part in the operation, the 18^th Army was by far the weakest as it comprised only four regular infantry divisions (Generalleutnant Karl von Tiedemann’s 207^th Division, Generalleutnant Friedrich Zickwolff’s 227^th Division, Generalleutnant Friedrich Koch’s [from 30 April 1940 Generalleutnant Walter Behschnitt’s] 254^th Division and Generalleutnant Josef Folttmann’s [from 10 January 1940 Generalleutnant Gerhard Kauffmann’s 256^th Division), assisted by three reserve divisions (Generalleutnant Moritz Andreas’s 208^th Division, Generalleutnant Ernst Schaumburg’s 225^th Division and Generalleutnant Hans von Sommerfeld’s 526^th Division) which would not take part in the fighting. Six of these divisions were 'third-wave' formations raised only in August 1939 from territorial Landwehr units: they had few regular officers and little fighting experience apart from those who were World War I veterans. Like those of the Dutch army, most German soldiers (88%) were insufficiently trained. The seventh division was the 526^th Division, which was purely a security formation without serious combat training. The German divisions, each with a nominal strength of 17,807 men, were half as large again as their Dutch counterparts and possessed twice their effective firepower, but even so the necessary numerical superiority for a successful offensive was simply lacking.

To remedy this, assorted odds and ends were used to reinforce the 18^th Army. The first of these was the only German cavalry division, Generalleutnant Kurt Feldt’s 1^st Kavalleriedivision. These mounted troops, accompanied by some infantry, were to occupy the weakly defended provinces to the east of the IJssel river and then try to cross the Afsluitdijk (enclosure dike0. A simultaneous landing in Holland near Enkhuizen was to be attempted, using barges to be captured in the small port of Stavoren. As both efforts were unlikely to succeed, the mass of regular divisions was reinforced by SS-Gruppenführer Paul Hausser’s SS-Verfügungsdivision (including the SS Standarte 'Der Führer', SS Standarte 'Deutschland' and SS Standarte 'Germania') and the SS Standarte 'Der Führer', which would all serve as assault infantry to breach the Dutch fortified positions. Even so, this added only one and one-third divisions to the German side of the balance-of-forces equation.

In order to ensure a victory the Germans resorted to unconventional means. The Germans had trained two airborne and air-landing assault divisions. The first of these, Generalmajor Kurt Student’s 7^th Fliegerdivision, consisted of paratroopers while the second, Generalmajor Hans Graf von Sponeck’s 22^nd Luftlande-Division, consisted of air-landing infantry. Initially the plan was that the main German assault was to take place in Flanders, and it was expected these troops would be used for an attempt to cross the Scheldt river near Ghent. When this part of this operation was cancelled, it was decided to use the airborne forces to obtain an easy victory in the Netherlands. On the invasion’s first day, the airborne troops would attempt to secure the airfields around the Dutch seat of government, The Hague, and then capture that government, together with the Dutch high command and Queen Wilhelmina. This 'Festung Holland' plan had been developed by Hitler personally as an embellishment of an earlier idea to let an envoy offer 'armed protection of the Dutch neutrality' as what would in effect become a German protectorate. In the event that this did not create the desired immediate collapse, the bridges at Rotterdam, Dordrecht and Moerdijk would simultaneously be secured to allow a mechanised force to relieve the airborne troops from the south. This force was to be Generalmajor Dr Alfred Ritter von Hubicki’s 9^th Panzerdivision. This was the only German armoured division with only two tank battalions, one of them understrength, in its single tank regiment, and the division’s tank strength was just 141. The intention was that the division should exploit a breach in the Dutch lines created by the 254^th Division and 256^th Division to link with them to constitute General Albert Wodrig’s XXVI Corps, on the axid from Gennep to 's-Hertogenbosch. At the same time an offensive would be undertaken against the Grebbelinie in the east by the 207^th Division and 227^th Division, united as General Christian Hansen’s X Corps, to engage the main bulk of the Dutch field army. The expectation was that despite their lack of numerical superiority, the forces would force the Dutch back to the eastern front of the Vesting Holland, or indeed beyond it. If the Dutch did not capitulate on the first day, the 18^th Army expected to enter the Vesting Holland on the third day from the south over the Moerdijk bridges and thereby ensure victory; there was no strict timetable for the total destruction of the Dutch forces. A peculiar aspect of the command structure was that the airborne attack was solely a Luftwaffe operation, so the airborne forces would initially not be under operational command of the army. The attack on Rotterdam was ultimately to be an army operation and considered by it as the Schwerpunkt (focal point) of the campaign in the Netherlands. The 18^th Army saw the air landings as primarily subservient to the advance of the XXVI Corps.

Of all the undertakings within 'Gelb', this most strongly embodied the concept of a Blitzkrieg as the term was then construed as a strategischer Überfall (strategic assault). Moreover, like 'Gelb' itself, it involved a high-risk strategy.

German civilians and troops generally disliked the idea of violating Dutch neutrality. German propaganda therefore justified the invasion as a reaction to a supposed Allied attempt to occupy the Low Countries, similar to the justification used by the German empire to invade Belgium in World War I.

Some German officers were averse to the Nazi régime and were also uneasy about the invasion. One such officer was Oberst Hans Oster, an [w]Abwehr (military intelligence) officer, who began in March 1939 to pass information to his friend, the Dutch military attaché in Berlin, Majoor Gijsbertus J. Sas. This information included the date on which 'Gelb' was to be launched, and Sas informed the Allies via other military attachés. However, several postponements while the Germans waited for favourable weather conditions led to a series of false alarms, which rendered the Dutch government and others somewhat sceptical of the information despite the fact that Sas’s prediction of the date of the attack on Denmark and Norway had proved accurate. Although he indicated a German armoured division would try to attack the Vesting Holland from North Brabant and that there was a plan to capture the queen, the Dutch defensive strategy was not adapted and it was not understood that these were elements of a larger scheme. On 4 May Sas again warned that an attack was imminent, and this in fact coincided with a warning from Pope Pius XII. When on the evening of 9 May Oster again 'phoned his friend saying just 'Tomorrow, at dawn', the Dutch forces were put on alert.

On the morning of 10 May, the Dutch awoke to the sound of aircraft engines as Germany launched 'Gelb' and attacked the Netherlands, Belgium, Luxembourg and France, and in the case of the neutral Low Countries without a declaration of war.

In the night the Luftwaffe had already violated Dutch airspace as bombers of Oberst Martin Fiebig’s Kampfgeschwader 4 'General Wever' crossed it and disappeared to the west, giving the Dutch the impression that the operation was directed at the UK. But over the North Sea the bombers of the KG 4 and other units turned back to the east to deliver a surprise attack on the Dutch airfields, together with the other wings. The bombers of the KG 4 hit the naval airfield at De Kooy, destroying 35 aircraft, most of them trainers. Fiebig himself was shot down and spent five days as a Dutch prisoner of war. The KG 4 also hit Amsterdam-Schiphol, where the Dutch lost a third of their medium bombers, and The Hague airfields where the I/KG 4 destroyed half of the 21 defending fighters to assist Oberstleutnant Walter Loebel’s KG 30 'Adler' and Oberst Walter Lackner’s KG 54 'Totenkopf' in attacks upon ports and communications. The KG 4 lost 11 Heinkel He 111 twin-engined medium bombers on 10 May and as well as three Junkers Ju 88 twin-engined bombers; and the KG 30 and KG 54 lost another nine bombers. The single-engined fighters of Major Hans Hugo Witt’s Jagdgeschwader 26 'Schlageter' and twin-engined heavy fighters of Oberstleutnant Joachim-Friedrich Huth’s Zerstörergeschwader 26 'Horst Wessel' shot down 25 Dutch aircraft in air combat for the loss of nine of their own number, and in total General Albert Kesselring’s Luftflotte II claimed 41 Dutch aircraft destroyed. The Dutch were left with just 70 aircraft by the end of the day. They claimed most of the German aircraft destroyed on 10 May and, divided over Dutch territory, continued to tackle the Luftwaffe wherever and whenever possible, claiming 13 victories over German fighters by 14 May.

Immediately after the bombardments, between 04.30 and 05.00 paratroopers dropped near the airfields. Dutch anti-aircraft batteries shot down many Junkers Ju 52/3m three-engined transport aircraft of the Luftwaffe’s Transportgruppen, and even more were wrecked during or after landing. In the whole of the campaign, the Germans lost 224 Ju 52/3m transport aircraft out of the 430 such aircraft deployed for the delivery of the German airborne forces.

The attack on The Hague ended in an operational failure. The paratroopers were unable to capture the main airfield at Ypenburg in time for the air-landing infantry to land safely. Although one armoured car had been damaged by a bomb, the other five such Landsverk vehicles, assisted by machine gun emplacements, destroyed the 18 Ju 52/3m machines of the first two waves, killing many of their occupants. When the runway was blocked by wrecks, the remaining waves aborted their landings and tried to find alternatives, often putting down their teams in meadows or on the beach, thus dispersing the troops widely. The small auxiliary airfield of Ockenburg was only lightly defended, and fell at once to German attack. The airfield of Valkenburg was likewise quickly occupied, the morale of the defenders shaken by the bombardment. However, the runway was still under construction and the level of the ground water had not yet been lowered: aircraft landing there sank into the soft soil. None of the airfields was thus capable of receiving substantial reinforcements. In the end the paratroopers had occupied Ypenburg but failed to advance into The Hague, their route being blocked by hastily grouped Dutch troops. Early in the afternoon the German airborne troops were dispersed by fire from three Dutch artillery batteries, and other Dutch batteries likewise drove away the German occupants from the other two airfields, the surviving airborne troops taking refuge in nearby villages and mansions.

The German attack on Rotterdam was much more successful. A group of 12 Heinkel He 59 twin-engined floatplanes, crammed with two platoons of troops, landed in the heart of the city and unloaded assault teams which seized the Willemsbrug, a bridge over the Nieuwe Maas, to form a bridgehead. At the same time the military airfield of Waalhaven, to the south of the city on the island of IJsselmonde, was attacked by airborne forces. A Dutch infantry battalion was stationed here, but so close to the airfield that the paratroopers landed near its positions and a confused fight ensued. The first wave of Ju 52/3m transport aircraft suffered no losses, and transports continued to land. In the end the Dutch defenders were overwhelmed and the German troops, steadily growing in number, began to move to the east to occupy IJsselmonde and eventually to make contact with the paratroopers tasked with occupying the vital bridge at Dordrecht. Although the Royal Netherlands navy intervened, the torpedo boats Z 5 and TM 51 attacking the Willemsbrug and the destroyer Van Galen later steaming up the Nieuwe Waterweg to bombard the airfield at short range, this resulted only in Van Galen foundering after being bombed. A plan to commit the gunboats Flores and Johan Maurits van Nassau was thereupon abandoned. At the Island of Dordrecht, the Dordrecht bridge was captured but in the city itself the garrison held out. The long Moerdijk bridges over the broad Hollands Diep estuary, connecting the island to North Brabant province, were captured and a bridgehead fortified on the southern side.

Executing a plan approved by Hitler, the Germans tried to capture the IJssel and Maas river bridges before they could be destroyed, using 'Brandenburger' commando teams of Hauptmann Dr Theodor von Hippel’s Bau-Lehr-Bataillon zbV 800 which had begun to infiltrate over the Dutch border ahead of the main advance, with some of their men arriving during the evening of 9 May. In the course of the night of 9/10 May they approached the bridges: several teams had a few men dressed as Dutch military police pretending to bring in a group of German prisoners in an effort to fool the Dutch detonation teams. Some of these 'military police' were real Dutchmen, members of the Nationaal-Socialistische Beweging, the Dutch Nazi party. Most of these attempts failed and the bridges were blown, on two occasions with 'Brandenburger' troops on therm. The main exception was the Gennep railway bridge, across which an armoured train immediately passed, followed by a troop train, both driving right through the Peel-Raamstelling at Mill and unloading an infantry battalion behind the Dutch defence line.

The Dutch released reports of German soldiers in disguise to the international news agencies. This caused a 'fifth column' scare, especially in Belgium and France. However, unlike the later situation in those two countries, in the Netherlands there was no mass exodus of civilian refugees, clogging the roads. In general, the German troops behaved in a civilised manner towards the Dutch population, forming neat queues at the shops to buy goods, such as chocolate, which was rationed in Germany.

After the generally failed assaults on the bridges, the German divisions began their attempts to cross the IJssel and Maas rivers. In general, the first waves were destroyed for lack of insufficient preparatory fire on the Dutch pillboxes. At most places a secondary bombardment destroyed the pillboxes and the infantry divisions then crossed the river after building pontoon bridges, but in some places, such as Venlo, the attempt was aborted. At Arnhem, the SS Standarte 'Der Führer' (mot.) led the assault and on that day advanced to the Grebbelinie, followed by the 207^th Division.

Even before the armoured train arrived, it had already been planned that the Dutch III Corps would be withdrawn from behind the Peel-Raamstelling, taking with it all the artillery apart from 36 8 Staal pieces. Each of the corps' six regiments was to leave one battalion behind to serve as a covering force, together with 14 'border battalions'. The group was the so-called 'Peel Division'. This withdrawal was originally planned for the first night after the invasion, under cover of darkness, but in the face of the speed of the German advance an immediate retreat was ordered at 06.45 so that the III Corps did not become entangled with German troops. The corps joined Brigade G, whose six battalions were already occupying the Waal-Lingelinie, and was thus brought up to strength again, but saw no further fighting.

The Light Division, based at Vught, was the only manoeuvre force the Dutch army possessed and its planned withdrawal had been similarly executed one day early. Its regiments had cycled across the Maas and Waal river bridges and then turned left through the Alblasserwaard when it was decided in the afternoon to use it in a counterattack on the German airborne landing on IJsselmonde. It reached the Noord river, which separates the Alblasserwaard from IJsselmonde, during the evening, and there discovered that the sector near the only bridge, built in 1939, was not strongly occupied by the airborne troops as the Germans had not known of its existence because of their outdated maps. It was decided to postpone a crossing until the next day, to gather sufficient forces. No attempt was made to establish a bridgehead.

Meanwhile, at about 22.00 during the evening of 10 May, French reconnaissance elements using Panhard 178 armoured cars had started to arrive at the Dutch border, forming a vanguard for the French 1ère Division Légère Mécanisée. This formation operated, with the 25ème Division d’Infanterie Mécanisée on its left, on the northern flank of the French 7ème Armée with the task of ensuring contact between the Vesting Holland and Antwerp. Attempts to co-ordinate the French advance with Kolonel Leonard Johannes Schmidt, the military commander of the Dutch troops in North Brabant, were largely unsuccessful as, apart from the fact that he could not be reached that day, the Dutch defences in that area were already collapsing. At Mill, the 256^th Division at first could not exploit the opportunity offered by having a battalion in the defenders' rear because it failed to locate it. When a first attack by forward elements had been repulsed, a full assault on the main defence line was initially postponed to the next day because most of the German artillery had not yet crossed the single pontoon bridge over the Meuse river, where a traffic jam had developed after the bridge had been damaged by an incident. During the early part of the early evening, in a sudden change of plan, it was decided to attack even though there was no artillery support except for one battery of 105-mm (4.13-in) howitzers. An unrequested Ju 87 dive-bomber attack also happened to hit the Mill sector just before the advance served to rout some Dutch defenders, creating a weak section in the line from which the Dutch troops were dislodged. The Germans were slow to exploit the breakthrough, but at 20,30 Schmidt ordered the abandonment of the Peel-Raamlinie, his men being instructed to fall back to the west and improvise a new defence line on the Zuid-Willemsvaart canal.

In the north, by the end of the day the 1^st Kavalleriedivision had reached the line between Meppel and Groningen, delayed by logistical problems and Dutch demolition teams which had blown 236 bridges. Dutch troop strength in that area was weak.

In the extreme south, the six border battalions in the province of Limburg delayed the advance of the 6^th Army only slightly. Before 12.00 the area had been overrun and the strategic city of Maastricht had surrendered, opening the way for the German feint offensive into central Belgium. The Germans failed to capture the main bridge intact, however, and this forced them to delay the crossing of by Generalleutnant Georg-Hans Reinhardt’s 4^th Panzerdivision until the next day.

On 11 May, Winkelman was faced with two priorities. First of all, he wished to eliminate the German airborne forces, for though the German strategic assault had failed, he feared a further German build-up via Waalhaven and saw the German possession of the Moerdijk bridges as a serious impediment to the movement of Allied reinforcements to the Vesting Holland. The second priority was closely related to the first: making it possible for the French to create a strong defensive line in North Brabant in order to connect the Vesting Holland with the Allied main force in Belgium. As he had withdrawn most of his troops from the area, Winkelman had only limited means available to influence this process, which was thus left largely to local commanders.

In both respects, little was achieved on this day. The planned counterattack by the Light Division against the airborne troops on IJsselmonde failed. The bridge over the Noord river had been prepared just in time for defence by the German paratroopers, and it proved impossible to force it. Several attempts to cross the river by boat managed only to establish a few isolated bridgeheads, and at 10.15 the Light Division was given permission to break off the crossing at this point and ordered to shift its axis of attack by reinforcing Dutch troops on the Island of Dordrecht, where it arrived that night. After clearing the Island of Dordrecht, the division was to advance into IJsselmonde over the Dordrecht bridge in order to reach Rotterdam.

Earlier in the day, Dutch battalions had made two to carry out an attack against the western flank of the German perimeter. The first battalion, withdrawn from the Belgian border, partly crossed the Oude Maas river at Oud-Beijerland and Puttershoek, and tried to storm the bridge at Barendrecht into IJsselmonde; the second battalion, taken from the Vesting Holland’s forces positioned at the Hoekse Waard, had crossed the Dordtse Kil to the Island of Dordrecht on the previous day, using the ferry at Wieldrecht, and now tried to expand its bridgehead. Although its crossings were successful, the advance of the first battalion was executed only hesitantly and was then surprised by German counterattacks and dispersed. The second battalion was likewise surprised, and many of its men were taken prisoner. During the afternoon, a French reconnaissance unit, the 5ème Groupe de Reconnaissance de Division d’Infanterie, with the assistance of a Dutch border battalion attempted an attack on the southern Moerdijk bridgehead, but the armoured cars of 6ème Cuirassiers with which it was reinforced were heavily attacked by dive-bombers and forced to retreat.

In Rotterdam, although reinforced by an infantry regiment, the Dutch failed to dislodge the German airborne troops from their bridgehead on the northern bank of the Maas river. Despite permission from Student, the German commander in Rotterdam refused to evacuate this bridgehead and the few German defenders held fast in a single office building, protected by a canal in front of them and covered by fire from the southern bank. The two remaining Dutch bombers failed to destroy the Willemsbrug. The German forces involved in the attack of the previous day on The Hague also held out, and this none of the attempts to eliminate the isolated groups, totalling some 1,600 paratroopers and air-landed infantry, met with success.

In North Brabant, the Dutch situation deteriorated swiftly. The commanders of the 7ème Armée had expected that Dutch resistance on the Maas river and the Peel-Raam Positie, by a force about five divisions strong, would have gained them at least four days to create a defensive line near Breda. They were unpleasantly surprised to learn that the best three divisions had been moved to the north and that the remaining forces were already in full retreat. Its withdrawal from the Peel-Raam Positie to the Zuid-Willemsvaart canal, some 6.2 to 18.5 miles (10 to 30 km) to the west, meant that the 'Peel Division' had to abandon its well-entrenched positions and the little artillery available in exchange for a totally unprepared line. Moreover, the eastern bank of the canal was higher than the western bank, providing excellent cover for the attackers. Finally, the order to withdraw did not reach the troops at Mill, and this caused one sector of the canal, near Heeswijk, to be left undefended. As this sector contained a bridge which was not demolished, the Germans were effortlessly able to cross the canal at about 13.00. A second crossing at Erp, this time opposed, led to a general collapse of the Dutch line. By the end of 11 May, the Germans had crossed the Zuid-Willemsvaart canal at most places and the 'Peel Division' had largely disintegrated. The plan of Schmidt to concentrate his forces on the line between Tilburg and 's-Hertogenbosch thus came to nothing. As the French refused to advance farther to the north-east than Tilburg, apart from some reconnoitring armoured cars that went as far as Berlicum, this created a dangerous gap. Knowing the general Dutch weakness in the region, Winkelman requested the British to send a corps to reinforce Allied positions in the area and also to bomb Waalhaven airfield.

All the efforts in the south were made on the assumption the Grebbelinie would be able to beat off attacks on its own: its reserves had even been shifted in part to the counterattack against the airborne forces. However, there were some indications that a problem was developing in this sector. Motorised elements of the SS Standarte 'Der Führer', moving ahead of the 207^th Division, had reached the southernmost part of the Grebbelinie in front of the Grebbeberg, on the evening of 10 May. This sector of the main defence line had no floodings in front of it, and had therefore been chosen as the division’s main axis of attack. It was protected by a line of outposts manned by two infantry companies. At about 03.30 on 11 May, German artillery started to shell the outposts, and at dawn there followed an attack by two battalions of the SS Standarte 'Der Führer'. As the German shelling had cut the telephone lines, no artillery support could be requested by the Dutch defenders, whose efforts were further hampered by the fact that the terrain had not yet been cleared of vegetation and this provided the attackers with good cover. At 12.00 a breakthrough was accomplished at the extreme north of the outpost line and the Dutch positions were then slowly rolled up. The outnumbered and more poorly armed Dutch companies resisted as best they could, but by evening all the outposts were in German hands. The commander of the II Corps, Generaal-majoor Jacob Harberts, failed to react adequately. He did not realise that motorised SS troops had been involved in the attack, and believed that the outposts had been surrendered to a small probing force through the cowardice of the defenders. Harberts ordered a night counterattack by the 4^th Division’s single reserve battalion, but this was abandoned as on its approach the battalion was engaged by Dutch troops manning the main line who had not been notified of its approach, leading to much confusion, and an engineer bridge necessary to cross the Grift stream was not brought forward in time. However, heavy preparatory Dutch artillery fire had the unintended effect of causing the Germans to abandon their own plans for a night attack.

Meanwhile, in the North, the 1^st Kavalleriedivision advanced through the province of Friesland toward the final Dutch fallback line, the Wonsstelling, reaching Sneek in the evening. Most Dutch troops had been evacuated from the north over the Afsluitdijk.

On the morning of 12 May, Winkelman remained moderately optimistic. He still assumed a firm defence line could eventually be established in North Brabant with the help of the French, and expected good progress could be made in eliminating the airborne forces, but was not aware of any special danger to the Grebbelinie. The coming day would see Winkelman’s hopes dashed.

In the previous two days, the ]e]9^th Panzerdivision had seen little action. It crossed the Maas river early in the morning of 11 May, but that day was unable to advance quickly over roads congested with the supply trains of the infantry divisions. The armoured division was under orders to link with the airborne troops as soon as the Peel-Raam Positie had been breached by the infantry forces and, as the entire Dutch front had dissolved, the conditions were favourable for such an attempt. In this the division would not be hindered by the French forces. Because the 6^th Army was threatening its right flank and there was no time to prepare a defence line, Gamelin ordered the 7ème Armée to withdraw its left flank. The 2ème Brigade Légère Mécanique, part of the 1ème Division Légère Mécanique, which had arrived at Tilburg, now retreated to the south. Also, the 25ème Division d’Infanterie Motorisée at Breda advanced no farther to the north than the Mark river. As the initial order to occupy the Geertruidenberg sector had not been implemented, the route to the Moerdijk bridges would not be blocked and the German armoured division would not be engaged by its stronger French mechanised counterpart. Reconnaissance elements of the 9^th Panzerdivision effectively exploited this opportunity: at dawn, to the north of Tilburg near Loon-op-Zand, they surprised Schmidt and took him prisoner. The Dutch troops in the province thereby lost all unified command. Shortly after 12.00 German armoured cars had penetrated 18.5 miles (30 km) farther to the west and made contact with the southern Moerdijk bridgehead, isolating the Vesting Holland from the Allied main force. At 16.45 the division reached the bridges. The northern part of that force would not long remain in the region, however, for at 13.35 Gamelin ordered a complete withdrawal from North Brabant to Antwerp of all French troops, which would now limit themselves to rear-guard actions.

The Light Division tried systematically to retake the Island of Dordrecht by advancing on a broad front, using four battalions with only limited artillery support. On its left flank, where there was almost no German presence, the advance went according to plan. The battalion on the right flank, however, encountered an attacking German force of battalion strength under instruction from Student to circle round the outskirts of the city and to relieve the Dutch pressure on his troops holding the Dort bridges. In confused street fighting the Germans were successful in blocking the battalion; the other Dutch units then halted their advance at about 12.00. Although higher command soon ordered a better concentration of forces instead of some mopping-up action, for lack of any clear lines of command, no subsequent attack materialised that day.

In Rotterdam and around The Hague again little was done against the paratroopers. Most Dutch commanders, still afraid of a presumed 'fifth column', limited themselves to security measures: they had been ordered to attempt no attack at anything above company strength.

While the situation in the south was becoming critical, in the east the Germans made a first successful effort to dislodge the Dutch defenders on the Grebbeberg. After a preparatory artillery bombardment in the morning, at about 12.00 one battalion of the SS Standarte 'Der Führer' attacked an 875-yard (800-m) sector of the main line, occupied by one Dutch company. Exploiting the many dead angles in the Dutch fields of fire, the battalion soon breached the Dutch positions, which had little depth. A second battalion then expanded the breach to the north. Dutch artillery, though equal in strength to that of the Germans, failed to bring sufficient fire on the Germans' infantry concentrations, instead limiting itself largely to interdiction. Some 875 yards (800 m) to the west was a stop line, a continuous trench system from which the defenders were intended to fight an active defence by staging local counterattacks. For lack of numbers, training and heavy weapons, however, the Dutch attacks failed against the SS troops. By the evening the Germans had brought the heavily forested area between the two lines under their control. Spotting a weak point, one of the SS battalion commanders, SS-Obersturmbannführer Hilmar Wäckerle, suddenly attacked with a hastily assembled force of about company strength. In what was for this campaign a rare instance of infiltration tactics, Wacherle’s force broke through the stop line, quickly advancing 1 mile (1.6 km) to the west before being halted by a fallback line along the Rhenen railway. The breakthrough caused a panic among the defenders, most of whom now abandoned the stop line, but as Wäckerle had been offered no time to co-ordinate his action with other units, the breakthrough was not further exploited. Order was restored at the stop line and the SS company became isolated and surrounded. The Germans' earlier general advance later caused the main line to be abandoned for a distance of more than 2 miles (3.2 km) to the north because the troops there feared an attack from their rear.

It had been well understood by the Dutch that the forces occupying the Grebbelinie would in themselves lack the strength to repel all attacks, so they were intended to delay an offensive long enough for reserves to reinforce them. As a result of the failure on the previous day to understand that the German main assault was imminent, these reserves would not arrive in time to intervene in the fight at the defence zone between the two trench systems. This was all the more serious as the stop line had no depth and lacked shelters to accommodate enough troops to stage a strong frontal counterattack. In the late evening it was decided to execute a flank attack from the north on the following day.

In the north, the Wons Positie constituted a bridgehead at the eastern end of the Afsluitdijk: it had a long perimeter of about 5.6 miles (9 km) to enclose an area of land of a size sufficient to receive a large number of retreating troops without making them them acutely vulnerable to air attack. On 12 May, units with a combined strength of only two battalions were still present, so the line was held only weakly. This was exploited by the first German unit to arrive, the single bicycle-mounted battalion of the 1^st Kavalleriedivision. At 12.00 this battalion quickly penetrated the Dutch line in a concentrated attack, forcing the defenders to withdraw to the Afsluitdijk. For some time the German advance cut their escape route by land, and they escaped by water from the small port of Makkum, taking the last remaining vessels on the eastern side of the IJsselmeer. This denied the Germans any craft for a crossing attempt, and the plan to do so was now abandoned.

During the afternoon, Winkelman received information about armoured forces advancing in the Langstraat region on the road between 's-Hertogenbosch and the Moerdijk bridges. He still fostered hopes that those forces were French, but the announcement by Radio Bremen at 23.00 that German tanks had linked with the paratroopers brought an end to this hope. At last Winkelman began to understand the essence of the German strategy. He ordered the artillery batteries in the Hoekse Waard to try to destroy the Moerdijk bridges and sent a spe