On 26 August German 2nd Panzer Group secured a bridgehead on the Desna's eastern bank near Novhorod-Siverskyi which threatened the eastern flank of 21st Army. Kuznetsov ordered a withdrawal over the river Desna. Unfortunately Kuznetsov did not inform the neighbouring Soviet units about his decision. Because of that 40th Army was forced to abort its attack on the German bridgehead near Novhorod-Siverskyi and the army commander, Major-General Kuzma Podlas, ordered a retreat to the southeast. Thus 21st Army, between South Western Front's 40th and 5th Armies was cut off from the forces of Bryansk Front. Kuznetsov can't be blamed for that decision because his army was at that point already beaten by German forces and in full retreat. In this situation on 6 September Kuznetsov's army was placed under the command of Southwestern Front. By then the advance by 2nd Panzer Group had forced a gap between South Western Front and Bryansk Front, and 21st Army, continuing to retreat to the south, became caught up in a vast encirclement that became the Battle of Kiev (1941). During the second week of September a significant portion of 21st Army was able to escape eastwards through gaps in 2nd Panzer Group's lines between Priluki and Piriatin, but the bulk of the army found itself, together with the rest of South Western Front, in a tightening encirclement east of Kiev. Only a few thousand soldiers, mainly from 21st Army and 5th Army, together with 500 men from Kuznetsov's headquarters staff, escaped from the final encirclement of South Western Front in the second half of September.