By 15th-16th July, 1st Panzer Group’s 48th Panzer Corps had achieved a decisive breakthrough near Kazatin where it had been battling the 6th Army’s 4th Mechanised Corps, and headed towards Kirovograd. Simultaneously, 14th Panzer Corps (slightly to the south) headed south towards Pervomaisk; thus forming the inner encircling arm threatening 6th, 12th and 18th Armies. Meanwhile the German 17th Army broke through the Stalin line near Bar, and by 18th July had crossed the Bug and formed a bridgehead around Vinnitsa. The 11th Army’s 30th Corps also advanced east from Mogilev-Podolsky. On the extreme south wing the 4th Rumanian Army broke out of its beachhead on the Prut River and, with the German 54th Infantry Corps, captured Kishinev. The 54th was ordered to cross the Dniester at Dubossary (to threaten the rear of Southern Front) while 4th Rumanian Army headed for Odessa.
By now the Stavka and Southwestern Front realised the danger was not to the Kiev forces, but to Southwestern Front’s south flank. They ordered a limited withdrawal of the 6th, 12th and 18th Armies, and ordered the 9th Army’s 2nd Mechanised Corps to move north and block the 1st Panzer Group’s advance south. This was the second and last mechanised corps that Southern Front had available to send north to assist Southwestern Front. However, these measures proved to be too little and too late. By 20th July 48th Panzer Corps had broken through and captured Monastyriche; effectively severing the escape route of the 6th and 12th Armies. The 2nd Mechanised Corps was all that stood between 48th Panzer Corps and German forces further south. Southwestern Front immediately ordered 26th Army to attack south-westwards and assist the 6th and 12th Armies to escape, while the latter were ordered to breakout eastwards and link up with 26th Army. The 26th Army launched a ferocious attack from the Cherkassy area into the exposed flank of the 1st Panzer Group, but Rundstedt had already marched the 17th Army’s 4th Infantry Corps eastwards and then south to support the panzer’s thrust south. Over five days the fighting continued with 26th Army suffering massive casualties as its infantry repeatedly attacked 4th Infantry Corps without armour or air support.
Meanwhile, only the Germans made significant advances as 14th and 48th Panzer Corps pressed south towards Pervomaisk to link up with the German 17th and 11th Armies. Further south the 11th Army’s 30th infantry Corps had reached Balta by 25th July which threatened to drive a wedge between 18th and 9th Armies of Southern Front (and push 18th Army into the forming Uman pocket). 18th Army’s 48th Rifle Corps counter-attacked in conjunction with 9th Army’s 2nd Cavalry Corps on 28th July but 30th infantry Corps held its ground, and by 1st August 30th Infantry Corps continued to advance eastwards. 11th German Army continued piling on the pressure however with 54th Infantry Corps also attempting to breakout of its bridgehead over the Dniester at Dubossary (to the south-west of Balta).
On 2nd August the 48th Panzer Corps’11th Panzer Division linked up with 17th Army’s 101st Light Division (52nd Infantry Corps) south-east of Uman. At around the same time the 14th Panzer Corps’ 16th Panzer Division linked up with German and Hungarian troops at Pervomaisk. The 6th and 12th Armies, and a large part of 18th Army were sealed in a pocket between Uman and Pervomaisk. Under continuous attack from 17th and 11th Army, the Uman pocket didn’t last long and was liquidated by 8th August. Despite the best efforts of the Soviet 26th Army to break open the pocket, barely 11 000 men escaped. By 8th August the Uman pocket was destroyed with 103 000 POWs taken. The Uman pocket was a major defeat for Southwestern and Southern Fronts because there were at least 24 divisions lost, even though the prisoner yield was relatively low compared to the pockets captured by Army Group Centre. The fact that the average Soviet division in the pocket was down to around 4 000 men is illustrative of the intensity of fighting and the fact that the forces in the pocket fought desperately to breakout before surrendering. It is estimated that another 90-100 000 Red Army soldiers actually perished in the Uman pocket. In addition to loss of troops, the whole south flank of Southwestern Front and the northern flank of Southern Front were now shattered, making any defence of the territory west of the Dnepr untenable.
By early August the newly mobilised Soviet 37th and 38th Armies had taken up positions on the Dnepr River at Kiev and Kremenchug. (A new 6th and 12th Army would shortly be assembled at Kharkov and Dnepropetrovsk with newly mobilised divisions). On 25th July, Rundstedt ordered 3rd Panzer Corps to leave its defensive positions on the Irpen River opposite Kiev and move south-eastwards along the Dnepr River line towards Cherkassy and Kremenchug. Evidently Rundstedt was already planning to regroup 1st Panzer Group in preparation for a breakout across the Dnepr River between Cherkassy and Kremenchug. This left only 6th Army’s 29th Infantry Corps to face 37th Army (around Kiev), and 51st and 17th Infantry Corps to face the 5th Army. This meant a direct assault on Kiev was now very difficult: with only three corps available to face the Soviet 5th and 37th Armies dug in across a major river. Perhaps sensing that the German forces would be focused on Uman, Kirponos ordered 5th Army to launch a surprise attack against 51st and 17th Infantry Corps. The attack force was comprised of the 5th Army’s 15th and 31st Rifle Corps, the remnants of the 9th and 22nd Mechanised Corps, and 1st Airborne Corps. The attack went in near Malin on 1st August and continued for five days. Although the Soviets managed a five mile advance the German line remained unbroken. Meanwhile the 29th Infantry Corps had attacked and by 5th August it had surprisingly managed to push 37th Army as far back as the outer suburbs of Kiev.
On the south wing, the Southern Front’s 9th Army and badly damaged 18th Army were ordered to fall back to the Bug as soon as it became obvious that the Uman pocket was irrecoverable. This was because they were now totally exposed to a continued German advance south and subsequent isolation. With great difficulty, Southern Front started to withdraw the bulk of 9th Army towards Nikolayev and 18th Army eastwards across the Bug towards Nikopol. These withdrawal orders were timely because 14th Panzer Corps was already moving south along the east side of the Bug River, and on 6th August elements of the panzer corps pushed back the flank guard (2nd Cavalry Corps) and captured Voznesensk.
Meanwhile, the Rumanian 4th Army had closed in on Odessa by 5th August and started encircling the fortified port. As the Black Sea Fleet was far stronger than any Axis naval presence in the Black See, the Odessa garrison was well supplied and even reinforced (to 86 000). The Red Army and Navy personnel defending Odessa had already been ordered to fight to the last man.
In many respects the achievements of Army Group South from 22nd June to 5th August actually exceeded the more ‘spectacular’ achievements of Army Group Centre. Unlike Army Group Centre, at the beginning of the campaign Army Group South was facing an enemy superior in manpower, and vastly superior in terms of combat aircraft and tanks. In June 1941 the Southwestern Front had such a concentration of forces that it has led historians (and other commentators) to conclude that Stalin was preparing a pre-emptive strike from the Ukraine into Southern Poland and Rumania in 1941. This will not be discussed here; suffice to say that a detailed examination of Southwestern Front’s forces, their state of readiness, and their deployment, does not support the pre-emptive strike in 1941 hypothesis. What Stalin was planning in 1942 is more difficult to assess.
Despite the odds against Army Group South, in a period of 45 days they had absolutely decimated Southwestern and to a lesser degree Southern Front. Over 24 divisions had been completely destroyed out of 80 divisions originally in the Kiev Special and Odessa Military Districts. Even worse, the average strength of the surviving pre-war rifle divisions was around half of the authorised levels, despite very large numbers of mobilised replacement riflemen arriving at the front. In terms of heavy weapons and particularly transport, all the surviving divisions were well below half strength. The greatest losses were amongst the tank forces and VVS. Out of the original 5 465 tanks and 2 059 combat aircraft available on 22nd June, only a few hundred of each remained.
In early August 1941 Southwestern Front still had around 750 000 personnel on strength, (compared to 907 000 on 22nd June) but this was due to replacements and newly mobilised armies being mobilised and deployed east of the Dnepr. Perhaps Army Group South’s greatest achievement is that it forced the Stavka to mobilise and deploy no less than six new armies south of Kursk and west of Belgorod in July and August. These were the 37th, 38th, 40th, 2nd/6th, 2nd/12th and 51st Separate (in the Crimea) Armies. All these armies were therefore drawn away from the cental Smolensk-Moscow axis (where nine new armies were mobilised and deployed in July and August).