On February 11, the Russians began to shell the fortified formations around Erzurum. Fierce fighting erupted. Ottoman battalions of 350 men had to defend against Russian battalions of 1,000 men. There were few reinforcements for the beleaguered Ottomans. In three days, the Russians had managed to reach the heights overlooking the Erzurum plain. It was now obvious to the Third Army's leaders that the town had been lost. The Ottoman units began to retreat from the fortified zones at the front and to evacuate the town of Erzurum.