In January 1915, two months after Turkey entered World War I on the side of the Central Powers, Russia appealed to Britain to defend it against attacks by the Ottoman army in the Caucasus. Lord Kitchener, Britain's secretary of state for war, told Churchill, first lord of the Admiralty, that no troops were available to help the Russians and that the only place where they could demonstrate their support was at the Dardanelles, to prevent Ottoman troops from moving east to the Caucasus. First Sea Lord John Fisher advocated a joint army-navy attack. The naval attack of March 18, 1915, was a disaster, as undetected Turkish mines sank half of the joint Anglo-French fleet sent against the Dardanelles. After this failure, the Allied command switched its focus to a landing of army troops on the Gallipoli Peninsula, with the objective of securing the Dardanelles so that the Allied fleet could pass safely through and reconnoiter with the Russians in the Black Sea. On April 25, British, French, Australian and New Zealander troops landed on the Gallipoli Peninsula. The Turkish forces were well prepared to meet them, however, as they had long been aware of the likelihood of just such an invasion. The Australian and New Zealand Army Corps (ANZAC) was devastated by some of the best-trained Turkish defenders, led by Mustafa Kemal, the future President Ataturk of Turkey. Meanwhile, the British and French also met fierce resistance at their landing sites and suffered two-thirds casualties at some locations.