Serbian and French troops finally made a breakthrough in September 1918 in the Vardar Offensive , after most of the German and Austro-Hungarian troops had been withdrawn. The Bulgarians were defeated at the Battle of Dobro Pole , and by 25 September British and French troops had crossed the border into Bulgaria proper as the Bulgarian army collapsed. Bulgaria capitulated four days later, on 29 September 1918.  The German high command responded by despatching troops to hold the line, but these forces were far too weak to reestablish a front.  The disappearance of the Macedonian Front meant that the road to Budapest and Vienna was now opened to Allied forces. Hindenburg and Ludendorff concluded that the strategic and operational balance had now shifted decidedly against the Central Powers and, a day after the Bulgarian collapse, insisted on an immediate peace settlement.  Ottoman Empire Main article: History of the Ottoman Empire during World War I See also: Middle Eastern theatre of World War I Australian troops charging near a Turkish trench during the Gallipoli Campaign The Ottomans threatened Russia's Caucasian territories and Britain's communications with India via the Suez Canal . As the conflict progressed, the Ottoman Empire took advantage of the European powers' preoccupation with the war and conducted large-scale ethnic cleansing of the indigenous Armenian , Greek , and Assyrian Christian populations, known as the Armenian Genocide , Greek Genocide , and Assyrian Genocide .    The British and French opened overseas fronts with the Gallipoli (1915) and Mesopotamian campaigns (1914). In Gallipoli, the Ottoman Empire successfully repelled the British, French, and Australian and New Zealand Army Corps (ANZACs). In Mesopotamia , by contrast, after the defeat of the British defenders in the Siege of Kut by the Ottomans (1915–16), British Imperial forces reorganised and captured Baghdad in March 1917. The British were aided in Mesopotamia by local Arab and Assyrian tribesmen, while the Ottomans employed local Kurdish and Turcoman tribes. 
Mehmed V greeting Wilhelm II on his arrival at Constantinople Further to the west, the Suez Canal was defended from Ottoman attacks in 1915 and 1916; in August, a German and Ottoman force was defeated at the Battle of Romani by the ANZAC Mounted Division and the 52nd (Lowland) Infantry Division . Following this victory, an Egyptian Expeditionary Force advanced across the Sinai Peninsula , pushing Ottoman forces back in the Battle of Magdhaba in December and the Battle of Rafa on the border between the Egyptian Sinai and Ottoman Palestine in January 1917.  Russian armies generally had success in the Caucasus. Enver Pasha , supreme commander of the Ottoman armed forces, was ambitious and dreamed of re-conquering central Asia and areas that had been lost to Russia previously. He was, however, a poor commander.
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