who had hitherto inflicted a series of defeats upon the forces of the Ottomans and their allies, being cut off from supply lines, outnumbered, outgunned and isolated, forcing them to fight and flee towards British lines in northern Mesopotamia. General Yudenich, the Russian commander from 1915 to 1916, drove the Turks out of most of the southern Caucasus with a string of victories. During the 1916 campaign, the Russians defeated the Turks in the Erzurum offensive, also occupying Trabzon. In 1917, Russian Grand Duke Nicholas assumed command of the Caucasus front. Nicholas planned a railway from Russian Georgia to the conquered territories so that fresh supplies could be brought up for a new offensive in 1917. However, in March 1917 (February in the pre-revolutionary Russian calendar), the Tsar abdicated in the course of the February Revolution, and the Russian Caucasus Army began to fall apart. The Arab Revolt, instigated by the Arab bureau of the British Foreign Office, started June 1916 with the Battle of Mecca, led by Sharif Hussein of Mecca, and ended with the Ottoman surrender of Damascus. Fakhri Pasha, the Ottoman commander of Medina, resisted for more than two and half years during the siege of Medina before surrendering in January 1919. The Senussi tribe, along the border of Italian Libya and British Egypt, incited and armed by the Turks, waged a small-scale guerrilla war against Allied troops. The British were forced to dispatch 12,000 troops to oppose them in the Senussi campaign. Their rebellion was finally crushed in mid-1916. Total Allied casualties on the Ottoman fronts amounted 650,000 men. Total Ottoman casualties were 725,000, with 325,000 dead and 400,000 wounded. Italian Front Although Italy joined the Triple Alliance in 1882, a treaty with its traditional Austrian enemy was so controversial that subsequent governments denied its existence and the terms were only made public in 1915. This arose from nationalist designs on Austro-Hungarian territory in Trentino, the Austrian Littoral, Rijeka and Dalmatia, which were considered vital to secure the borders established in 1866. In 1902, Rome secretly agreed with France to remain neutral if the latter was attacked by Germany, effectively nullifying its role in the Triple Alliance. When the war began in 1914, Italy argued the Triple Alliance was defensive in nature and it was not obliged to support an Austrian attack on Serbia. Opposition to joining the Central Powers increased when Turkey became a member