Britain's fears of war with Germany were realised in 1914 with the outbreak of the First World War. Britain quickly invaded and occupied most of Germany's overseas colonies in Africa. In the Pacific, Australia and New Zealand occupied German New Guinea and Samoa respectively. Plans for a post-war division of the Ottoman Empire, which had joined the war on Germany's side, were secretly drawn up by Britain and France under the 1916 Sykes–Picot Agreement. This agreement was not divulged to the Sharif of Mecca, who the British had been encouraging to launch an Arab revolt against their Ottoman rulers, giving the impression that Britain was supporting the creation of an independent Arab state.

When did the First World War begin?