The northern attack towards Rava-Ruska commenced on the 13 July 1944. The 1st Ukrainian Front forces easily broke through near Horokhiv. The weakened Wehrmacht XLII.Armeekorps, managed to withdraw relatively intact using reinforced rearguard detachments. By nightfall, the 1st Ukrainian Front's 13th Army had penetrated the German lines to a depth of 20 kilometers. The 1st Ukrainian Front's breakthrough occurred to the north of the XIII.Armeekorps.
On the 14 July 1944, the assault with the objective of liberating Lviv was begun to the south of the XIII.Armeekorps, which had positions near the town of Brody, an area of early Red Army failure in the war. Red Army units had punched through the line near Horokhiv to the north, and at Nusche in the south, leaving the XIII corps dangerously exposed in a salient. The northern pincer towards Rava-Ruska now began to split and turned several units of the 13th Army south, in an attempt to encircle XIII.Armeekorps.
The northern forces soon encountered weak elements of the 291. and 340.Infanterie-Divisions, but these were quickly swept aside. On 15 July, Generaloberst Nehring, realising his 4. Panzer-Armee was in jeopardy, ordered his two reserve divisions, the 16. and 17. 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 attack soon bogged down. The massively superior Red Army forces soon forced the 16.Panzer and 17.Panzer divisions to join the retreating infantry divisions. Konev ordered Mobile Group Baranov into the breach to help exploit the breakthrough. The Mobile group, under cover of air support, advanced quickly, and over the next three days managed to capture the town of Kamionka Strumilowa as well as to seize and hold a bridgehead on the western bank of the Buh river, cutting the XIII.Armeekorps' line of communication and cutting off their path of retreat.