The war against Ottoman Turkey evolved piecemeal and over disparate areas. In the initial phase, 1914-15, with the exception of Gallipoli, only relatively small forces were involved and many of these did not originate in Britain. By the end of the war, 500,000 troops had been committed against Ottoman Turkey and Egypt had become the greatest base for British troops outside the homeland. There were four areas of British involvement against the Turks and although the operations in all four areas overlapped at one time or another, they will be dealt with roughly in chronological order: Mesopotamia, Gallipoli, Sinai and the Arabian Peninsula. The continued existence of the Ottoman Empire, in light of a putative German victory or a compromise peace, or its transformation into a militant Republic tied to a victorious Imperial Germany, after 1918, is a counter-factual people can all live without.