envisaged the envelopment of the city from north and south, the southern arm of the envelopment being based on an advance to the north by an army within the Barvenkovo Pocket off 38th Army's left flank. This offensive opened on 12 May. The attacks north of Kharkov were held by German forces, and in the south the Germans responded by launching an offensive of their own against the shoulders of the Barvenkovo Pocket. The southern shoulder was attacked by powerful mechanised forces on 17 May, and on the northern shoulder the positions of 38th Army's left flank in the Balakliya area were attacked two days later. By 23 May the Soviet forces in the Barvenkovo Pocket, including two entire field armies, a mechanised group, part of a third army and part of 38th Army, had been cut off. By the end of the month the encircled force had been destroyed, less than one in ten of the surrounded personnel being able to effect an escape, and Moskalenko was left defending roughly the same positions in the Kupyansk area that 38th Army had occupied in November 1941. Yet despite his losses, Moskalenko's army, facing the right wing of the German Sixth Army and the left flank of First Panzer Army, at this time included eight rifle divisions amply supported by armour. On the morning of 28 June the main German strategic offensive of 1942 (Case Blue) opened with an attack from the Kursk area towards the Don at Voronezh. The German objective was to advance down the right bank of the Don to cut in behind Southwestern Front and so isolate it from its sources of supply. By 6 July this objective had become clear to Soviet high command and the next day, in order to avoid a major encirclement, Southwestern Front was authorised to retreat to the east. As the days passed this retreat became increasingly chaotic and by 12 July Moskalenko was struggling to maintain close control over his forces, which were in danger of being surrounded at Markivka. One week later and 100 kilometres further to the southeast, part of 38th Army was surrounded at Millerovo. The rest of Moskalenko's army was able to cross to the relative safety of the left bank of the Don, but on 23 July most of its residual forces were assigned to 21st Army, 38th Army was formally disbanded, and Moskalenko's headquarters