The Russian revolution left the front in eastern Turkey in a state of flux. In December 1917, a truce was signed by representatives of the Ottoman Empire and the Transcaucasian Commissariat. However, the Ottoman Empire began to reinforce its Third Army on the eastern front. Fighting began in mid-February 1918. Armenians, under heavy pressure from the Ottoman army and Kurdish irregulars, were forced to withdraw from Erzincan to Erzurum and then to Kars, eventually evacuating even Kars on 25 April. As a response to the Ottoman advances, the Transcaucasian Commissariat evolved into the short-lived Transcaucasian Federation; its disintegration resulted in Armenians forming the Democratic Republic of Armenia on 30 May 1918. The Treaty of Batum, signed on 4 June, reduced the Armenian republic to an area of only 11,000 km2.