After five days of intense fighting, the Russian army defeats the Third Turkish Army to capture Erzerum, a largely Armenian city in the Ottoman province of Anatolia, on this day in 1916.
The Central Powers considered Turkey, which entered World War I in November 1914, a valuable ally for two reasons: first, it could threaten British interests in the Middle East, and second, it could divert Russian troops from the front in Europe to the Caucasus. Unfortunately for the Turks, the success of this second objective resulted in the loss of the Turkish province of eastern Anatolia to the Russians in 1916.
The brilliant Russian campaign of February 1916 was commanded by General Nikolai Yudenich, one of the most successful and distinguished Russian commanders of the war. On February 11, the Russian troops began their attack on Erzerum from the south, over Kop Mountain. Once the Russian forces broke through the Turkish lines to the south and began to attack other Turkish positions, the fall of Erzerum seemed inevitable. The Third Turkish Army began abandoning their equipment and retreating from their positions as the Russians entered the city. In total, the Russians captured more than 1,000 guns and artillery and took some 10,000 Turkish prisoners.
With the capture of Erzerum, arguably the strongest and most important fortress in the Turkish empire, the Russians had gained the upper hand in the battle for control on the Caucasus front. With this one victory, the Russians captured or controlled all the roads leading to Mesopotamia and Tabriz and, in essence, controlled western Armenia.
In the wake of the Bolshevik Revolution in Russia in 1917 and the subsequent armistice between Russia and the Central Powers, Erzerum was returned to Turkish control. The transfer of power was made official under the terms of the Treaty of Brest-Litovsk in March 1918.
Taken from: http://www.history.com/this-day-in-history/russians-capture-erzerum [16.02.2015]