'Astonia' was the British undertaking by Lieutenant General J. T. Crocker’s British I Corps of General H. D. G. Crerar’s Canadian 1^st Army within Field Marshal Sir Bernard Montgomery’s Anglo-Canadian 21^st Army Group to establish a bridgehead over the Seine river downstream of Rouen to facilitate the capture the major port of Le Havre, which was seen as an objective of great importance as it was thought to be capable of handling some 20,000 tons per day (10/12 September 1944).

By this time other Allied forces had pushed through to take the more significant harbour facilities at Antwerp, which were also closer to the fast-moving Allied front line, but nonetheless Le Havre had been declared by Adolf Hitler to be a Festung (fortress) that was to be held to the last man. In 'Astonia', the Allied objective was to secure the harbour facilities intact as thus facilitate the delivery of supplies to the Allied armies advancing to the east across western Europe. The Allies refused to allow the evacuation of the port city’s civilian population despite offers of free passage by the fortress commander, Oberst Dr Hermann-Eberhard Wildermuth.

From 26 August, British warships and warplanes blockaded the German enclave and a major preparatory bombardment killed more than 2,000 civilians as well as just 19 German troops. The land attack was undertaken under British command primarily by Canadian forces with specialised armoured support by 'funnies' of Major General Sir Percy Hobart’s British 79^th Armoured Division. The German garrison of about 11,000 men surrendered on 12 September. The port was found to have been badly damaged, but was reopened on 9 October.

On 6 June 1944, 'Neptune' (iii) saw the landing of Allied troops in Normandy as the start of the 'Overlord' campaign to began the liberation of France. On this day Allied aircraft laid a smoke screen off Le Havre to blind the German coastal artillery, and under cover of this smoke a torpedo boat flotilla and a patrol vessel flotilla departed the port. (In June 1944, Admiral Theodor Krancke’s Marineoberkommando West had a total of five torpedo boats, 50 minesweepers and 21 patrol vessels at Le Havre.) The German vessels fired 15 torpedoes in the waters off the Orne river estuary at 05.30, hitting and sinking the Free Norwegian destroyer Svenner and forcing several other ships to take evasive action. On 6 July, Allied ships reported an 'unusual object' passing through the 'Trout' line, which was the eastern flank of the invasion area. The object was engaged with gunfire but launched a torpedo and then moved away. Several more such 'unusual objects' appeared soon after this in a well-dispersed attack, and were also taken under fire. The devices managed to sink two minesweepers for a loss of nine of their own number sunk among 15 losses from all causes of the 26 that had departed Le Havre. It was later established that these were 'Neger' one-man midget semi-submersibles of the K-Verband. On the night of 7/8 July, 21 'Neger' craft left Le Havre: all of these were sunk, most of their operators being killed, in exchange for the sinking of the British minesweeper Pylades and the damaging of the Free Polish cruiser Dragon, which was scuttled off 'Sword' Beach.

Air Chief Marshal Sir Arthur Harris’s Bomber Command attacked Le Havre during the evening 14 June. A total 221 Avro Lancaster heavy bombers and 13 de Havilland Mosquitoes target markers of Nos 1, 3, 5 and 8 Groups carried out the command’s first daylight raid since the departure of No. 2 Group at the end of May 1943. The objectives were the S-boot and other light naval forces which represented a threat to Allied shipping off the Normandy beaches only some 30 miles (50 km) to the west. The attack was flown in two waves, one during the evening and the second at dusk. Most of the 228 aircraft in the first wave were of No. 1 Group and the 21156 aircraft in the second wave of No. 3 Group. Pathfinder aircraft provided marking by their normal methods for both raids. No unexpected difficulties were encountered, and the area of the naval port was accurately bombed by both waves, in which 1,880 tons of bombs were dropped, and few S-boote remained undamaged. No. 617 Squadron sent 22 Lancaster aircraft each carrying one 12,000-lb (5443-kg) Tallboy bomb together with three Mosquito marker aircraft to attack the concrete-covered S-boot pens just before the attack of the first wave: several hits were scored on the pens and one bomb penetrated the roof.

The operation was the largest day raid undertaken by RAF Bomber Command since the start of the war, and was regarded as an experiment by Harris, who was still reluctant to risk his squadrons to the dangers of daylight operations, but both waves of the attack were escorted by Supermarine Spitfire fighters of No. 11 Group and only one Lancaster was lost.

The reports available from Le Havre gave no details of damage to the naval vessels or facilities other than to mention the ravages considerables (considerable damages) inflicted on the port area by No. 617 Squadron’s bombs. The reports stressed the courage of the local civil and French naval fire brigades which continued to fight the fires caused by the first wave of bombing when the second wave attacked. The Nôtre Dame district, near the port, was devastated but the people there had been evacuated at an earlier date. Other districts were also hit, with 700 houses and a tobacco factory destroyed and the local jail damaged. Some 76 civilians were killed and another 150 injured. The fact remains, however, that most of the British bombs landed in the area of the harbour and that the S-boot threat to the invasion beaches from this port had been almost completely removed.

By coincidence, Le Havre’s anti-aircraft gun defences had been prohibited from firing in order to protect Luftwaffe aircraft in the area, and the bombing killed about 1,000 German marines, demoralised the survivors and destroyed about 15,000 tons (15,000 t) of shipping, comprising nine S-boote of the 5^th Schnellboots-Flottille and 9^th Schnellboots-Flottille which were sunk, two seriously damaged one and slightly damaged, three of the five torpedo boats sunk, along with 20 minesweepers and patrol boats, and 19 tugs. Several auxiliary vessels were also sunk and eight other vessels were damaged.

Some S-boote managed to reach Le Havre in the middle of June but by the end of July only six S-boote on the English Channel coast were operational. The Royal Navy formed a Support Squadron Eastern Flank as a group of small gun-armed vessels, which came inshore during the day to bombard land targets and patrolled offshore at night. This squadron fought many engagements with S-boote and K-Verband elements. On the night of 2/3 August, the Germans despatched 20 Linsen (explosive motor boat) sorties, more than 50 'Marder' midget submarine forays and several S-boote attacks with the new TIIId circling torpedo: most of these German craft were sunk. The night sorties by S-boote transferred to Le Havre after 6 June sank one motor torpedo boat, two LSTs, three merchant ships, two landing craft and two tugs for the loss of six [S-boote sunk and damage to 10 others.

Le Havre was the most important of the English Channel ports in northern France, and was indeed second only to Marseille on France’s southern coast among French ports in overall tonnage capacity. The port had 8.1 miles (13 km) of quays capable of receiving ocean-going ships. In 'Maple' from a time early in April, British aircraft and ships laid mines off Le Havre (as well as the smaller ports farther to the north-east) and these closed the port for long periods. Early in September, German troops of General Gustav-Adolf von Zangen’s 15^th Army held a swathe of coastal territory from Le Havre to Bruges in Belgium, which had been under attack by the Canadian 1^st Army since the start of September. The port of Le Havre has water on three sides: the English Channel to the west, the valley of the Lézarde river to the east and the Canal de Tancarville connecting Le Havre and the estuary of the Seine river, to the south. To the north of Le Havre, the ground rises steeply to high ground as far as the cliffs of Cap de la Hève and the coast to the north. The Lézarde and Fontaine river valleys cut the area into two plateaux, the northern plateau lying between the rivers and the southern plateau to the south and west of the Fontaine river, which overlooks the port. Some 3 miles (4.8 km) inland, the southern plateau is covered by the Fôret de Montgeon.

The Germans had dug an anti-tank ditch from the Lézarde river valley past Montivilliers to the coast at Octeville sur Mer. This ditch was covered by minefields, barbed-wire entanglements and concrete defensive positions. At the crest of the southern plateau, two fortified positions covered the town and harbour mouth, and the Grand Clos coastal artillery battery could engage approaching ships. The garrison had 115 guns, large numbers of machine-guns and mortars, large quantities of ammunition and a 90-day supply of consumables for 14,000 men. Near Fontaine La Mallet lay No. 8 Strongpoint, comprising several concrete gun emplacements, as the first of a series of such strongpoints covering the northern approaches to the port. The minefields and tank obstacles had been constructed hurriedly, and were superimposed on an earlier and unfinished scheme based on strongpoints. To the west of Strongpoint No. 8, the ground is unsuitable for tanks but from the strongpoint to the Lézarde river the ground is flat and unobstructed, with a gentle 200-yard (185-m) slope on each side, the plateaux on both sides being at the same height as the strongpoint, which commanded the stream. The anti-tank ditch was V-shaped in section, 22 ft (6.7 m) wide at the top and more than 12 ft (3.7 m) deep, but was not continuous.

The Allied invasion plan required that the Canadian 1^st Army on the 21^st Army Group’s left flank, was to cross the Seine river downstream of Rouen and turn to the north into the Le Havre peninsula and thus effect a right-handed flanking manoeuvre to capture Le Havre and its railway connections, Dieppe, Calais and Dunkirk. All of these were needed for the Allied logistic effort, which was otherwise dependent on the Normandy beaches and other ports increasingly distant to the west. during the night of 26/27 August, the crossing of the Seine river by the Canadian 1^st Army began, and Rouen was captured on 30 August, Crocker’s British I Corps used every means it could improvise to cross the lower reaches of the Seine river, which was not bridged, and Lieutenant General G. Simonds’s Canadian II Corps to cross farther upriver. The two corps were ordered to capture Le Havre and Dieppe respectively and then to clear the coastal belt as far as Bruges. On the other side of the front line, Generalfeldmarschall Walter Model’s Heeresgruppe 'B' ordered General Erich Brandenberger’s 7^th Army to abandon the lower reaches of the Seine river, and by 31 August von Zangen’s 15^th Army to hold a line from Dieppe to Neufchâtel, but the speed of the Allied advance forced a retreat to the Somme river. In 'Fusilade', Dieppe was entered without opposition by the Canadian 2^nd Division on 1 September, and the British 51^st Division walked into St Valery en Caux. The 51^st Division joined the 49^th Division outside Le Havre on 4 September. As the Canadian 1^st Army prepared its attack on Le Havre, the seaward approaches were blockaded closely by the Allied naval forces from 26 August: on this date the port was the most westerly still in German hands, and the Kriegsmarine tried to deliver supplies and to extract the ships still afloat. During the next four nights convoys departing Le Havre were attacked and a few ships managed to slip away. Nine ships were sunk, and by 30 August the port was empty.

It was on 14 August that Wildermuth assumed command of the fortress of Le Havre in succession to Generalmajor Hans Sauerbrey, and he later put the effective strength of the garrison at some 8,000 men out of a total of more than 11,000 men: Allied intelligence under-estimated at some 8,700 men (including 4,000 artillerymen, 1,300 naval personnel and 3,400 infantry of varying quality). Wildermuth had a Festungsstammabteilung (fortress cadre unit) comprising elements of Generalleutnant Wolfgang von Kluge’s 226^th Division and Generalleutnant Erwin Sander’s 245^th Division (one battalion of whose 36^th Grenadierregiment was the most effective part of the defence), one battalion of the 5^th Sicherungsregiment and the 81^st Festungsabteilung, both of very low fighting value, marines and some naval personnel. Some 50,000 French civilians remained in the city out of a normal population of about 160,000 persons. On 9 September, Wildermuth ordered that infantry attacks were to be resisted, even if only pistols were available, but in the face of armoured attacks, strongpoints which lacked anti-tank guns could surrender: thus, rather than fight to the last man, the garrison was to resist until the last anti-tank gun. Before the attack, the defenders were given an ultimatum and called upon to surrender, and Wildermuth countered by requesting that civilians should be evacuated, given that his orders from Hitler were to hold Festung Le Havre to the last man. Wildermuth appealed to British humanity and repeated his offer, even after the bombing campaign started, but was again refused. Crocker judged that the proposed two-day truce needed for the civilian evacuation would impose an unacceptable delay on the capture of the port.

A naval and air bombardment was planned for the 'softening' of Le Havre’s fortifications. The battleship Warspite and the monitor Erebus, carrying eight and two 15-in (381-mm) guns respectively, bombarded the port with more than 4,000 tons of shells over several days. On 5 September, Erebus was forced temporarily out of action by a hit from the Grand Clos battery, which had one 380-mm (14.96-in) and two 170-mm (6.7-in) guns. The port defences also had 44 medium and field guns and 32 Flak guns. The RAF Bomber Command day attack on 5 September was the first of seven raids. On the night of 6/7 September, a similar number of aircraft attacked, and another day raid was flown on 8 September by 109 aircraft. Another raid on 9 September had to be cancelled as a result of adverse weather, but the raids flown delivered about 4,000 tons of bombs. On 10 September, about 60 bombers attacked the Grand Clos battery in an undertaking followed by a bombardment from Warspite and Erebus, and these put the German guns out of action. RAF Bomber Command returned in the afternoon and dropped another 4,900 tons of bombs as the British divisional artillery and the 4^th Army Group Royal Artillery and 9^th Army Group Royal Artillery conducted counter-Flak bombardments during the raids. Before the ground attack, the RAF flew 1,863 Lancaster and Handley Page Halifax four-engined heavy bomber sorties and dropped more than 9,500 tons of bombs. The air and naval bombardments killed about 2,000 French civilians but only 19 Germans.

During the North-West European campaign between 6 June 1944 and 8 May 1945, British specialist armour was the responsibility of Hobart’s 79^th Armoured Division, with subordinate units attached to other formations for particular operations. (Though most of its core vehicles were derived from infantry tanks, the 79^th Armoured Division contained other vehicles two regiments of Kangaroo armoured infantry carriers, Sherman DD amphibious tanks, Buffalo tracked landing vehicles and Terrapin amphibious landing vehicles.) For 'Astonia', the 79^th Armoured Division provided Major General E. H. Barker’s 49^th Division with the 222^nd Assault Squadron RE (AVRE), two Crab squadrons of the 22^nd Dragoons and a Crocodile squadron of the 141^st Regiment Royal Armoured Corps. The division also had Brigadier W. S. Clarke’s 34^th Armoured Brigade and Lieutenant Colonel G. M. Churchill’s Canadian 1^st Armoured Carrier Regiment with 44 Kangaroos under command. In the I Corps plan, Phase I called for the 49^th Division to break through on the northern front, capture strongpoints to the south and cross the Fontaine river. In Phase Iia, Major General T. G. Rennie’s 51^st Division was to break through on the right, and in Phase IIb the 49^th Division was to capture the southern plateau. In Phase II the 51^st Division was to take the ground around Octeville and the heights to the north of Le Havre, and in Phase IV all these forces were to exploit opportunities any and every opportunity to capture the city.

To the east of Strongpoint No. 8, the German anti-tank ditch lay near the top of the slope down to the stream, with a minefield to its front. Brigadier M. S. Ekin’s British 56^th Brigade was to deliver the 49^th Division’s front. The attack plan was to penetrate the German defences and so create a breach through which additional forces could attack, then drive forward from these gains and capture the city. The two divisions' assault began at 17.45 on 10 September, with naval bombardment vessels engaging the coastal batteries defending the port and RAF bombers dropping an additional 5,000 tons of bombs 90 minutes before the start of the ground attack. With the assistance of specialist units of the 79^th Armoured Division and the 1^st Canadian Armoured Carrier Regiment, such as Kangaroo armoured personnel carriers and Sherman Crab mine-flail vehicles, the first part of the assault proceeded swiftly, with gaps cleared through the minefield and the anti-tank ditch breached. The 49^th Division penetrated the north-eastern section of the Le Havre perimeter first, followed by the 51^st Division attacking on its right from the north. The assault was costly for the specialised armour, for heavy rains had rendered the river banks considerably softer than the plateaux, slowing the flail tanks and other vehicles at their most vulnerable. The 79^th Armoured Division lost 34 Crab flail tanks, two command tanks and six AVRE heavy assault pioneer vehicles.

On the second day of 'Astonia', the attack continued with support from Hawker Typhoon fighter-bombers and more armoured vehicles, Faced with the threat of Churchill Crocodile flame-throwing tanks, the Germans' last outer defence strongpoints surrendered at 14.00. On the assault’s third day, the city centre was cleared by the infantry of both divisions, persuading Wildermuth to surrender at 11.45. Some 11,300 German troops were taken prisoner.

Despite the weather, the bombing had greatly hampered the defence of the port, and the final attack just before the ground operation began on 10 September, which benefited from the experience in 'Charnwood', caused much disorganisation among the defenders. 'Astonia' was thus a model combined operation in which the British advantage in set-piece attacks backed by massed firepower was efficiently exploited. Much emphasis had been placed on maintaining the momentum of the attack and on good timing, the usual caution in attack being relaxed to exploit any sign that the defenders were collapsing. While there had been few Allied casualties during the operation, the damage inflicted on the port’s infrastructure by the bombing and the German programme of demolitions had been severe, the docks and 15,000 buildings having been destroyed, but the port was open again by 9 October. Wildermuth claimed that the lack of anti-tank guns had prevented a long defence of the port, but other prisoners said that even the experience of war on the Eastern Front had been less of an ordeal than the bombing. Because of the scandal of friendly civilian casualties, Allied forces besieging Calais allowed the evacuation of civilians before this smaller port was attacked. The Germans held Dunkirk until their overall surrender on 8 May 1945.