Turkey joined the war on the side of the Germans in October 1914 and promptly closed the Dardanelles to Allied shipping. However, this backwater was a vital lifeline for Russia through which she could receive vital military aid from the western powers that was necessary if she was to remain in the war for any significant period. At the same time, the costly nature of the war on the Western Front was becoming apparent and there was a school of thought, led by Winston Churchill, First Lord of the Admiralty, that believed in an 'indirect approach' to attacking Germany's interests, via what later became known as the 'soft underbelly of Europe'.
The original plan was purely naval, in which the Anglo-French Fleet would force the Dardanelles. A preliminary bombardment of the shore batteries and mine sweeping began in February 1915. On 18 March, the Fleet entered the confined waters of the Dardanelles, struck an undetected minefield and came under heavy fire. After a protracted exchange of fire, the fleet withdrew, with the loss of three of sixteen battleships.
Admiral De Roebeck and General Sir Ian Hamilton concluded that to clear the Dardanelle batteries, the newly forming Middle East Expeditionary Force should land on the Gallipoli Peninsular without delay. In approving the plan, ministers in London were deferring to the men on the spot. However, a protracted land campaign was not envisaged by either the politicians or commanders.