Just two days after its navy suffered a demoralizing defeat against Turkish forces at the Dardanelles, the British government signs a secret agreement with Russia regarding the hypothetical post-World War I division of the former Ottoman Empire.
By the terms of the agreement, signed on March 20, 1915, Russia would annex the Turkish stronghold of Constantinople, the Bosporus Strait (a waterway connecting the Black Sea with the Sea of Marmara and marking the boundary between the Asian and European halves of Turkey), and more than half of the European section of Turkey. Britain also promised Russia future control of the Dardanelles (the crucially important strait connecting the Black Sea with the Mediterranean)—which the British navy had unsuccessfully attacked two days earlier—and the Gallipoli peninsula, the target of a major Allied military invasion (which would also result in failure) launched late the following month. In return, Russia would agree to British claims on other areas of the former Ottoman Empire and central Persia, including the oil-rich region of Mesopotamia.
The Anglo-Russian agreement of March 1915 illustrated the vast degree to which traditional relationships between nations had been changed by World War I. The agreement represented a complete turnaround from past British policy toward Russian control of Constantinople, which they previously thought threatened the British dominance in the region that had been achieved through its colonial administration of India. As part of a coalition including France, Sardinia and Turkey, Britain had in fact gone to war with Russia in the Crimean Peninsula in 1854 (a conflict known as the Crimean War) to prevent Russia from claiming Constantinople and the strait. In 1878, Prime Minister Benjamin Disraeli had sent the British fleet to the Dardanelles to warn the Russians away from Constantinople during the Russo-Turkish War. Now, in a secret agreement, Britain was promising away the very territory it had so assiduously defended—territory it was simultaneously trying desperately, with little success, to win.