'Blau' (iv) was the German northern portion of the summer offensive of 1942 against the Soviet forces on the Eastern Front later redesignated as 'Braunschweig' (28 June/24 July 1942).

After the failure of 'Barbarossa' and 'Taifun' (i) in the previous year, and the limited successes of the Soviet offensives of the winter of 1941/42 and spring of 1942, Adolf Hitler was determined that the German forces on the Eastern Front should regain both the strategic and operational initiatives and in the process gain major victories which would cripple the Soviets and also provide Germany with major resources in the south, most especially the oil of the Caucasus region which, Hitler now admitted, would be required for the effective German prosecution of the war of attrition that was now inevitable against the USSR.

By February 1942, the Oberkommando des Heeres had started to develop concepts for a major strategic campaign into the southern part of the USSR and with the Caucasus region as its principal objective. On 5 April 1942 Hitler laid out the key elements of the plan, now known as 'Blau', in the Führerweisung Nr 41. This laid it down that the main goals of the summer campaign on the Eastern Front were of a triple nature, in the form of the capture of Leningrad and a junction with the Finns by Generalfeldmarschall Georg von Küchler’s Heeresgruppe 'Nord' in the north, holding actions by Generalfeldmarschall Fedor von Kluge’s Heeresgruppe 'Mitte' in the centre, and the capture of the Caucasus region by Generalfeldmarschall Fedor von Bock’s Heeresgruppe 'Süd' in the south.

The immense Caucasus region, with the Caucasus mountains as it spine, extends between the Black Sea on its western side and the Caspian Sea on its eastern side. The area to the north-west of the mountains was a heartland for the production of grain, cotton and heavy farm machinery, and its two primary oilfields, at Maykop near the Black Sea and Grozny near the Caspian Sea, produced about 10% of all Soviet oil. The area to the north-east of the mountains, south-west of the Volga river between Stalingrad and its debouchment into the Caspian Sea at Astrakhan, was the essentially arid and resources-deficient Kalmyk Steppe. To the south of the mountains lay the densely populated region of the Transcaucasus, comprising Georgia, Azerbaijan and Armenia. This heavily industrialised area contained some of the largest oilfields in the world. Baku, the capital of Azerbaijan, was one of the richest, producing 80% of the USSR’s oil (some 24 million tons in 1942 alone).

The Caucasus was also a major source of coal and peat, and was also the location of large quantities of non-ferrous and rare minerals: the manganese deposits at Chiaturi were the richest single source in the world, yielding 1.5 million tons of ore (half of the USSR’s total production) every year. The Kuban north-western region of the Caucasus also produced very substantial quantities of essential foodstuffs in the form of wheat, maize, sunflower seed and sugar beet.

All of these resources were of vast significance for the German war effort. Of the oil Germany consumed every year in the late 1930s, some 85% was imported largely from the USA, Venezuela and Iran. When World War II started in September 1939, the British naval effectively isolated Germany from the Americas and the Middle East, leaving the country reliant on oil-rich European countries such as Romania. Germany’s need for imported oil is revealed by the fact that in 1938 only 33% of the 7.5 million tons of oil consumed by Germany came from domestic stocks. In the modern age, indeed, oil had been Germany’s constant grand strategic weakness, and by the end of 1941 Germany’s reserves had been almost totally exhausted, which left the country with only two significant sources of oil in he form of the country’s own synthetic production and the Romanian oilfields: the latter supplying 75% of Germany’s oil imports in 1941.

Aware of Germany’s declining oil reserves and fearful of Allied air attacks on Romania, now Germany’s only significant source of crude oil, Hitler’s strategy was increasingly driven by the need to protect Romania and acquire new resources, essential if Germany was to continue waging a prolonged war against a growing list of enemies. Late in 1941 the Romanians warned Hitler that their stocks were exhausted and they were unable to meet German demands. For these reasons, therefore, the Soviet oilfields were vital to Germany’s industrial and military capabilities within the context of an ever more global war, the growing power of the Allies after the USA’s entry into the war in December 1941, and the increasing list of shortages adversely affecting Axis resources.

As noted above, on 5 April Hitler had issued his Führerweisung Nr 41, which ordered a major offensive during the summer of that year to take Stalingrad and the Caucasus region in the southern part of the Eastern Front before the German army’s attention was refocused on the destruction of Leningrad in the northern part of the Eastern Front. The offensive was eventually launched on 28 June, some weeks later than had been planned as the German forces on the Eastern Front had first to defeat the Soviet spoiling offensives, launched in May, in the regions of Kharkov ('Izyum Bridgehead Offensive Operation' of 12/29 May) and Crimea ('Battle of the Kerch Peninsula' of 8/19 May). The Soviet offensive faltered after achieving only limited gains, and the Panzer forces assembled for 'Blau' (iv) then counterattacked and crushed Timoshenko’s forces, killing or capturing some 275,000 Soviet troops in 'Fridericus I'. At much the same time Generaloberst Erich von Manstein’s 11^th Army in Crimea had defeated a feeble offensive launched by the Crimea Front and then driven its remnants into the sea, killing or capturing another 150,000 Soviet soldiers, at the end of the 'Crimean Offensive Operation' (27 January/15 April).

Although the two Soviet offensives did succeed in delaying the start of 'Blau' (iv), they also severely weakened the Soviet forces in southern Russia and left them vulnerable to even greater defeat by 'Blau' (iv). Redesignated 'Braunschweig' (i) on 30 June, the 'Blau I' undertaking was schemed by von Bock’s Heeresgruppe 'Süd' before its division of 9 July into Bock’s (from 13 July Generalfeldmarschall Maximilian Reichsfreiherr von Weichs’s) northern Heeresgruppe 'B' and Generalfeldmarschall Wilhelm List’s southern Heeresgruppe 'A'.

The support for the undertaking was provided by Generaloberst Alexander Löhr’s Luftflotte IV, whose two primary elements were Generaloberst Wolfram Freiherr von Richthofen’s (from 1 July General Martin Fiebig’s) Fliegerkorps VIII and General Kurt Pflugbeil’s Fliegerkorps IV. The German air strength on the Eastern Front totalled 2,644 aircraft on 20 June 1942, this figure representing a 20% increase over the figure of one month earlier. During the campaigns of 1941, the majority of German air units operated over the central sector of the Eastern Front in support of Heeresgruppe 'Mitte', but by the middle of 1942 some 61% of the German air strength on the east Front (1,610 machines) was flying in support of Heeresgruppe 'Süd'.

The overall German plan was based on a three-axis offensive: 'Blau I' was to be an attack from Kursk to Voronezh and continuing to the south-east to shield the left flank of 'Blau II'; 'Blau II' was to be centred on Generaloberst Friedrich Paulus’s 6^th Army's advance from Kharkov and move in parallel with Generaloberst Hermann Hoth’s 4^th Panzerarmee to reach the Volga river at Stalingrad, whose capture was initially deemed unnecessary; and 'Blau III' in which Generaloberst Ewald von Kleist’s 1^st Panzerarmee was then to strike to the south-east in the direction of the lower reaches of the Don river with Generaloberst Richard Ruoff’s 17^th Army and General de corp de armatâ Constantin Constantinescu’s Romanian 4^th Army on its western and eastern flanks respectively.

The strategic objectives of the operation were the oilfields at Maykop, Grozny and Baku. As in 'Barbarossa', the movements of the three 'Blau' (iv) offensives were expected to result in a series of grand encirclements of Soviet troops.

In 'Blau I', Heeresgruppe 'Süd' (soon Heeresgruppe 'B'), using von Weichs’s 2^nd Army, Vezérezredes Gusztáv Jány’s Hungarian 2^nd Army and Generaloberst Herman Hoth’s 4^th Panzerarmee (totalling 17 German and six Hungarian divisions including three Panzer and two German motorised infantry divisions), was to advance from the area just to the east of Kursk to the line of the Don river between Livny and Rossosh, taking the vital city of Voronezh against the Soviet forces of General Leytenant Fyedor Ya. Kostenko’s South-West Front. Here the Axis infantry was to hold the new line against any Soviet counter-offensives from the north and east while the Panzer divisions under Hoth’s command advanced rapidly to the south-east. The operation was designed to provide the necessary left-flank protection for the 'Donets corridor' through which Paulus’s 6^th Army was to advance to Stalingrad in 'Blau II'.

Although 'Blau I' was to be undertaken at the height of summer, the German command nonetheless expected major supply and transport problems as a result of the distances involved and the region’s generally underdeveloped land communications system. The railway network was adequate for the delivery of only small quantities of matériel and supplies, and reliance was placed on three west/east spurs with railheads at Kursk, Kharkov and in the area of Gorlovka and Stalino. The northern spur at Kursk ran eastward to Voronezh, and in the south the railway continued eastward from the area of Gorlovka and Stalino to Stalingrad: the tracks of both the latter spurs had be relaid before the Germans could make effective use of these spurs. In the area of Kharkov there was no railway track to the east, and the movement of the 4^th Panzerarmee and the 6^th Army down the Don river could not be supported by use of the Voronezh/Millerovo railway that ran parallel with their axes as a portion of the track, between Voronezh and Svoboda, lay on the eastern bank of the Don river and was thus still in Soviet hands: Hitler specifically forbade any attempts to seize major bridgeheads on the eastern side of the river, so there was no possibility of completing German control of the railway. The only railway running into the Caucasus that was of value to the Germans crossed the Don river bridge at Rostov-na-Donu, which was still in Soviet hands.

Since maintenance of substantial land forces by rail transport was therefore likely to prove difficult, reliance had still to be placed on motor transport, but the availability of vehicles and fuel was no better than it had been during the previous summer, and the available vehicle capacity was less than would be demanded of it. For lack of rail or road transport, all the infantry divisions involved continued to advance at the speed of the walking horse.

The Germans' tactical intelligence of the Soviet forces was good, but their strategic intelligence continued to be poor although, to an extent at least, this was irrelevant as the German plan had been drafted without consideration of Soviet strategy and possible plans, or even of Soviet military dispositions. Whether or not the Soviet forces to the west of the Don river could be destroyed depended on the thinking current in the Soviet high command: if it insisted on holding fast, the Soviet forces were doomed, but if it had learned the lesson of its recent defeat between Kharkov and Izyum (12/29 May and including 'Fridericus I'), which was a Soviet reverse as great as the Germans were to suffer at Stalingrad, it was possible that the Soviet troops might escape across the Don river in relatively good order and thus come to pose a threat northern flank of the German offensive. A few weeks before, between the Donets and Oskol, the Soviet forces had escaped encirclement by withdrawing with skill and great alacrity.

On the Soviet side, the defeat between Kharkov and Izyum had left Timoshenko’s South-Western Direction weak and disorganised. There followed the usual regrouping and reorganisation of the higher command levels. The headquarters of the South-Western Direction was disbanded, Timoshenko reverting to command of the South-West Front, and the two flanking fronts, namely General Leytenant Filipp I. Golikov’s Bryansk Front and General Leytenant Rodion I. Malinovsky’s South Front, were taken under direct control of the Stavka. After the destruction of the Crimea Front, a new North Caucasus Front was created under the command of Marshal Sovetskogo Soyuza Semyon M. Budyonny.

The fact that a German offensive was imminent, and would probably fall on the Bryansk Front, at least initially, was appreciated in Moscow, but the Soviet strategic intelligence assessment regarded this attack as the preliminary to a major offensive directed along a north-eastern rather than south-eastern axis and therefore intended to outflank and encircle Moscow. The Soviet high command thus strengthened Golikov’s Bryansk Front with four tank corps (the equivalent of 10 infantry divisions and four tank brigades) in order to tackle the expected German offensive.

In fact launched farther to the south, and on a south-eastern rather than north-eastern axis as noted above, 'Blau I' caught the Bryansk and South-West Fronts unprepared and off balance. It is worth noting that in the period between 28 June and the end of November, the three 'Blau' (iv) offensives pitted some 1.3 million Axis troops (1 million Germans and 300,000 allies) with 1,900 tanks and 1,610 aircraft against 2.7 million Soviet troops (1.7 million at the front and 1 million in reserve) with 3,720 tanks and about 1,670 aircraft. The losses were about 1.013 million Axis troops and 2.2264 million Soviet troops, the latter in the form of 111,680 killed and missing, and 1.1147 million wounded.

It was at 02.15 on 28 June that von Bock’s forces, supported by the considerable air support of von Richthofen’s (from 1 July Fiebig’s) VIII Fliegerkorps, launched Hoth’s 4^th Panzerarmee in the direction of Voronezh with von Weiss’s 2^nd Army covering its northern flank. The attack fell on General Leytenant Nikolai P. Pukhov’s 13^th Army and General Leytenant Mikhail A. Parsegov’s 40^th Army, driving a great gap between them, and the Bryansk Front made the error of committing its tank corps to the fighting on a piecemeal basis, resulting in the destruction of these armoured formations.

Two days later, on the day that Hitler redesignated 'Blau I' as 'Braunschweig' (i), Paulus’s 6^th Army fell on General Leytenant Vasili N. Gordov’s 21^st Army and General Leytenant Dmitri I. Ryabyshev’s 28^th Army of the South-West Front, forcing them apart. By 2 July von Weiss’s troops had met those of Paulus near Stary Oskol and completed the first tactical envelopment, encircling parts of the 21^st and 40^th Armies and taking a large number of prisoners.

As noted above, the German offensive had two objectives. One was to confuse the Soviet leadership about about the ultimate goals of the 'Blau' (iv) campaign. There was widespread feeling by almost all observers, especially the Soviet high command, that the Germans would reopen their attack on Moscow during the summer of 1942. By attacking in strength toward Voronezh, near the site of the Germans' deepest penetration of the previous year, 'Blau I' would help to conceal the nature of the primary offensive taking place far to the south. The Soviet forces which would inevitably be sent to the area of 'Blau I' in order to bolster the defence of the area would not be able to move with the same speed as the Germans, who would then turn to the south and leave them behind. The other purpose was to provide an easily defended front line along the line of the Don river, providing a strong left flank that could be protected with relatively light forces.

The plan involved forces of Heeresgruppe 'Süd', at this time far to th north of its ultimate area of responsibility. The attack would be spearheaded by Hoth’s 4^th Panzerarmee. Hoth’s highly mobile forces were to strike eastward to Voronezh and then to turn to the south-east to follow the Don river south-eastward to Stalingrad. As the 4^th Panzerarmee moved out of Voronezh, the slower-moving infantry forces of the 2^nd Army following behind the Panzer army would have arrived to assume an essentially defensive posture along the river. The plan called for the 2^nd Army to reach Voronezh just as the 4^th Panzerarmee had cleared the city, and Hoth was under strict orders to avoid any urban fighting which might impede its progress.

The city was defended by the troops of the 40^th Army as part of the 'Valuiki-Rossosh Defensive Operation' (28 June/24 July) of General Nikolai F. Vatutin’s South-West Front.

Hoth’s powerful armoured forces moved forward with little delay on 6 July, and faced their only natural barrier before the city in the form of the Devitsa river, an arm of the Don river passing through Semiluki a short distance to the west. For reasons that remain unclear, the bridge over the Devitsa river had not been destroyed, and Hoth’s forces were able to sweep aside the local defence and reach the outskirts of Voronezh on 7 July. Still believing that the German strategic objective was Moscow, the Soviet high command started to move a tank army and two further infantry armies from its reserves toward the Voronezh area, and the Soviet forces then mounted a successful counterattack that pinned Hoth’s forces in the 1^st Battle of Voronezh.

At this point the 4^th Panzerarmee should have been relieved by the 2^nd Army, but this latter was still far to the west of this major Soviet industrial centre. Intense house-to-house fighting broke out, and Hoth continued to push forward while he waited. At one point Generalmajor Helmuth Schlömer’s 3^rd Division (mot.) advanced to the east and crossed the Dob river, but then turned back. The Soviet high command poured reserves into the city, and there emerged a situation not unlike that which later developed in Stalingrad a few months later, with German troops clearing the city street-by-street with flamethrowers while tanks provided fire support.

The 2^nd Army arrived only two days later, by which time the 4^th Panzerarmee was heavily engaged and could not extricate itself from the battle for some time. The 2^nd Army continued the battle until 24 July, when the final Soviet forces to the west of the Don river were defeated and the fighting ended. Hitler later came to believe that these two days, when combined with other avoidable delays on the German drive to the south-east, allowed Timoshenko to reinforce the Soviet forces in Stalingrad before the 4^th Panzerarmee could arrive and open the way to the capture of Stalingrad.

The German had committed 975,000 men and suffered the loss of 94,500 men including 19,000 killed or wounded, while the Soviets had committed 1.3 million men and suffered the loss of 370,000 men killed, 197,625 wounded and 80,000 taken prisoner.

The Soviet forces recaptured the city of Voronezh in the 2^nd Battle of Voronezh, itself part of the 'Voronezh-Kastornoye Offensive Operation' in January/February 1943.

Then, in the second week of the campaign, there began to develop a series of differences between Hitler and von Bock. Hitler intended that the Don river should provide left-flank protection for the 'Blau' (iv) offensives, and that all the armoured formations should move rapidly to the south-east, leaving the river line to be held by the minimum possible number of infantry divisions. In Führerweisung Nr 41 and in his order to Heeresgruppe 'Süd' on 12 April, Hitler had demanded the capture of Voronezh even though this lay a few miles beyond the Don river’s eastern bank. On 3 July Hitler was in two minds, however, and finally decided that it might not be necessary after all to take Voronezh. So Hitler left to von Bock the decision whether or not to take it, provided that the capture of the city did not delay the movement of the German armour to the south-east.

Hitler then began to become concerned about the slow pace of von Bock’s advance and, although he visited von Bock at this time and was affable, no sooner was he back at his headquarters at Rastenburg in East Prussia than his suspicions and criticisms once again surfaced. There were endless telephone calls between Hitler, von Bock, General Georg von Consternate (chief-of-staff of Heeresgruppe 'Süd'), Generalfeldmarschall Wilhelm Keitel (head of the Oberkommando der Wehrmacht) and Generaloberst Franz Halder (chief-of-staff of the Oberkommando des Heeres). von Bock was nervous of the possible threat posed by scattered Soviet tank forces to his south and had in fact become temporarily bogged down on the eastern bank of the Don river: given the great Soviet strength there (estimated at 20 infantry divisions with many tank formations) and the increasing Soviet pressure in the area of Voronezh, von Bock became reluctant to move his troops away to the south.

Thus the one corps of the 4^th Panzerarmee already despatched to the south had insufficient momentum to envelop the elements of the 21^st and 28^th Armies pulling back rapidly to the east under pressure from Paulus’s advance. By 8 July von Bock had released further armoured formations from Voronezh for the south, but within a day or so most of the Panzer formations had come to a halt near Tikhnaya Sosna as they ran out of fuel. Not before 13 July did the 4^th Panzerarmee reach Boguchar.

In all, von Weichs and Paulus took only 30,000 prisoners, which was nothing like the measure of success expected of such an offensive, and it was obvious that the larger part of the Soviet forces was escaping over the Don river.

The Oberkommando des Heeres did not order Heeresgruppe 'A' forward until 7 July, when it was already too late to destroy the Soviet forces to the west of the Don river: aware of the threat of envelopment from the north, the South-West and South Fronts were already in full retreat, great columns of troops harried by the Luftwaffe crossing the Don river at Kazansk and Yelansk.

The 1^st Panzerarmee crossed the Donets river on 8 July and three days later, having met and overcome only rearguard action, was approaching Starobyelsk on the Aidar river. On the same day Ruoff’s Armeegruppe 'Ruoff' () started to move forward against the forces of General Leytenant Rodion Ya. Malinovsky’s South Front, but made only slow progress in the face of widespread minelaying and determined rearguard action, while near Taganrog on the Mius river the Soviet army held on the approaches to Rostov-na-Donu.

The German offensive was still not achieving its primary aim, which was the destruction of the Soviet forces. von Bock tended to be over-concerned with the security of his left flank, and was frequently halted by torrential rain and lack of petrol. The Armeegruppe 'Ruoff' (17^th Army and Romanian 3^rd Army) lacked the strength to achieve anything of real value. On 9 July Hitler began to meddle in the battle down right down to the tactical level. Hoth and his 4^th Panzerarmee headquarters, still in the area of Voronezh, were instructed to move to the south into the area of Kantemirovka and assume control of General Leo Freiherr Geyr von Schweppenburg’s XL Panzerkorps of the 6^th Army, and use this formation in a short tactical encircling movement to meet with von Kleist in the area of Kamensk, cutting off the Soviet forces in the area of Millerovo. When Hoth arrived at Kantemirovka, however, he found that von Bock had ordered the Panzer corps to the east, down the Don river toward Stalingrad, and the tanks had already reached the Chir river near Bokovskaya, the point at which they were turned back to meet von Kleist. Thus only 14,000 prisoners were taken in the Millerovo encirclement.

Thus a mere two weeks into the 'Blau' (iv) operations, on 11 July, the Germans had begun to suffer major logistics difficulties, which slowed the pace of the advance. The 6^th Army was continually delayed by fuel shortages. Eight days later, on 20 July, shortages of fuel were still undermining operations, leaving many units unable to undertake what was demanded of them. Generalleutnant Hans Reichsfreiherr von Boineburg-Lengsfeld’s (from 20 July Generalmajor Erwin Mack’s) 23^rd Panzerdivision and Generalleutnant Bruno Ritter von Hauenschild’s 24^th Panzerdivision were each left stranded during this opening phase. As in the 'Weserübung' campaign in Norway during April 1940 and the 'Barbarossa' campaign of 1941, the Luftwaffe’s Junkers Ju 52/3m transport fleet delivered just sufficient in the way of supplies (including 200 tons of fuel per day) to keep the ground forces moving. The situation remained nevertheless difficult, and the German troops were forced to the expedient of recovering fuel from damaged or abandoned vehicles, and in some cases, of temporarily abandoning their tanks and other vehicles with heavy fuel consumption in order to continue their advance. This undermined the combat strength of the formations involved. Despite this impressive performance in just managing to keep the ground forces on the move, Löhr was replaced on 20 July by the more impetuous and offensively-minded von Richthofen.

Hitler was desperately seeking the destruction of an elusive enemy. Senior Soviet prisoners had revealed that there were no Soviet forces of any consequence to the west of the Don river, a fact confirmed by Luftwaffe air reconnaissance, but Hitler was certain that the Soviet forces must have withdrawn to the lower Don in the area lying north of Rostov-na-Donu. Disregarding his Stalingrad strategy and his own previous orders, Hitler then prepared a huge encirclement battle to trap the forces north of the Don river’s mouth.

On 13 July Hoth’s 4^th Panzerarmee was transferred from Heeresgruppe 'B' to List’s Heeresgruppe 'A', ordered to cross the lower part of the Don river at Konstantinovka and move to the west toward Rostov-na-Donu and the Sea of Azov. The 1^st Panzerarmee was to turn right, cross the Donets river once again and move west along the northern side of the lower reaches of the Don river. Meanwhile Heeresgruppe 'B' was to protect the northern flank of Heeresgruppe 'A'.

Both Panzer armies started to move west, away from Stalingrad, at times almost crippled as much by lack of fuel as by the thick mud caused by heavy rain, when the South Front’s resistance to the Armeegruppe 'Ruoff' suddenly ended. Even so, the Soviet troops withdrew with some skill, having already evacuated much of their heavy equipment.

All the German orders were changed yet once more on 13 July, when Hitler, having the day before dismissed with contempt Halder’s objection to the concentration of so much armour to so little purpose, and having rejected Halder’s alternative that the lower reaches of the Don river should be crossed on a broad front, adopted this alternative as his own and ordered that Heeresgruppe 'B' should halt its advance on Stalingrad. von Bock foresaw little success for an envelopment which was strong in the centre and weak on the flanks (a criticism of the Oberkommando des Heeres’s instruction of 11 July which directed the 1^st Panzerarmee and 4^th Panzerarmee to Kamensk and Millerovo. But criticism of the Oberkommando des Heeres was deemed to be criticism of Hitler, who had been railing for a week against von Bock for the delay at Voronezh.

On the afternoon of 13 July Keitel telephoned von Bock to tell him that Hitler had decided to reallocate command of Heeresgruppe 'B' to von Weichs, and that Keitel himself strongly advised von Bock to ask to be relieved of his appointment on account of sickness. When von Bock demanded to know the grounds for his dismissal he was told that Hitler was dissatisfied with the vehicle fuel supply arrangements in Heeresgruppe 'B': yet as von Bock and von Weichs both pointed out, it was the quartermaster department of the Oberkommando des Heeres which was solely responsible for supply.

On 15 July von Weichs assumed command of Heeresgruppe 'B', in turn passing command of the 2^nd Army to Generaloberst Hans von Salmuth.

By this time during the middle of July, in the belief that the main Soviet threat had been eliminated, Hitler was keenly aware of his ground forces' desperate shortage of fuel and the ever more pressing need to meet all the ambitious objectives of 'Blau' (iv) in a timely fashion. In these circumstances Hitler amended the operational case he had made in Führerweisung Nr 41 by the issue of Führerweisung Nr 45 on 23 July. Heeresgruppe 'Süd' had already been divided in Heeresgruppe 'A' and Heeresgruppe 'B', and Hitler now ordered Heeresgruppe 'A' to advance into the Caucasus and capture the oilfields in 'Edelweiss' (i) and Heeresgruppe 'B' to press its advance toward the Volga river and take Stalingrad in 'Fischreiher'.

There is no evidence Hitler was opposed by, or even received complaints, from Halder or anyone else, about Führerweisung Nr 45 until a time in the following month. The new directive created enormous logistical difficulties, for Hitler now demanded that both army groups advance along different axes with divergent logistics routes. The whole of the German logistics system on the Eastern Front was already at breaking point, with acute shortages of ammunition and fuel highly evident, and it would be impossible to advance using the present conservative supply rates he demanded. The divergent axes imposed on the two army groups would also open between the armies an operationally dangerous gap which the Soviets could exploit. Moreover, no effective deployment of tactical resources was made in light of the task at hand: this is highlighted by the fact that the three Italian mountain divisions of Generale di Corpo d’Armata Gabriele Nasci’s Corpo d’Armata Alpino, of General d’Armata Italo Gariboldi’s Armata Italiana in Russia, was not deployed into the Caucasus mountains with Heeresgruppe 'A' but instead remained with Paulus’s 6^th Army for service on essentially flat terrain. Heeresgruppe 'A' was therefore expected to operate in mountain terrain with only three mountain divisions and two infantry divisions unsuited to the task.