The northern forces soon encountered weak elements of the 291st and 340th Infantry Divisions, but these were quickly swept aside. On 15 July, "Generaloberst" Nehring, realising his 4th Panzer Army was in serious jeopardy, ordered his two reserve divisions, the 16th and 17th Panzer Divisions to counterattack near Horokiv and Druzhkopil in an attempt to halt the Soviet northern assault. The two divisions could muster only 43 tanks between them and despite their best efforts, the German counterattack soon bogged down. The massively superior Red Army forces soon forced the two Panzer divisions to join the retreating infantry divisions. Konev ordered Mobile Group Baranov into the breach to help exploit the breakthrough. The Mobile Group advanced quickly, under cover of air support, and over the next three days managed to capture the town of Kamionka Strumilowa and to seize and hold a bridgehead on the western bank of the Southern Bug River, thus cutting the XIII Army Corps' line of communication and cutting off their path of retreat.