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On January 8, 1916, Allied forces stage a full retreat from the shores of the Gallipoli Peninsula in Turkey, ending a disastrous invasion of the Ottoman Empire. The Gallipoli Campaign resulted in 250,000 Allied casualties and greatly discredited Allied military command. Roughly an equal number of Turks were killed or wounded.
In early 1915, the British government resolved to ease Turkish pressure on the Russians in the Caucasus front by seizing control of the Dardanelles channel, the Gallipoli Peninsula, and then Istanbul. From there, pressure could be brought on Austria-Hungary, forcing the Central Powers to divert troops from the western front. The first lord of the Admiralty, Winston Churchill, strongly supported the plan, and in February 1915 French and British ships began bombarding the Turkish forts guarding the Dardanelles.
Beginning April 25, British, Australian, and New Zealand troops landed on the Gallipoli Peninsula, while the French feinted a landing on the opposite coast to divert Ottoman forces. The Australians and New Zealanders were devastated by the Turkish defenders, who were led by Mustafa Kemal, the future President Ataturk of Turkey. Meanwhile, the British likewise were met with fierce resistance at their Cape Helles landing sites and suffered two-thirds casualties at some locations. During the next three months, the Allies made only slight gains off their landing sites and took terrible casualties.