On 12 July, the garrison's parent formation, 3rd Panzer Army, counter-attacked. 6th Panzer Division, organised into two groups ("Pössl" and "Stahl") attacked eastwards from outside the encirclement (the divisional commander and Colonel-General Reinhardt personally accompanied the advance group). The opposing Soviet forces, taken by surprise and hampered by extended lines of supply, were not able to hold the cordon and 6th Panzer's forces were able to advance some 50 km to link up with forward elements from the Vilnius garrison. A fierce battle on the banks of the Neris ensued as men of the Polish Home Army unsuccessfully attempted to stop the relief troops.