On April 25, 1915, a week after Anglo-French naval attacks on the Dardanelles end in dismal failure, the Allies launch a large-scale land invasion of the Gallipoli Peninsula, the Turkish-controlled land mass bordering the northern side of the Dardanelles.
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. During the next three months, the Allies made only slight gains off their landing sites and sustained terrible casualties.
To break the stalemate, a new British landing at Suvla Bay occurred on August 6, but the British failed to capitalize on the largely unopposed landing and waited too long to move against the heights. Ottoman reinforcements arrived and quickly halted their progress. Trenches were dug, and the British were able to advance only a few miles.
In September, Sir Ian Hamilton, the British commander, was replaced by Sir Charles Monro, who in December recommended an evacuation from Gallipoli. On January 8, 1916, Allied forces staged a full retreat from the shores of the peninsula, ending a disastrous campaign that resulted in 250,000 Allied casualties and a greatly discredited Allied military command, including Churchill, who resigned as first lord of the Admiralty and accepted a commission to command an infantry battalion in France.