The island would serve Britain as a key military base for its colonial routes. By 1906, when the Famagusta harbour was completed, Cyprus was a strategic naval outpost overlooking the Suez Canal, the crucial main route to India which was then Britain's most important overseas possession. Following the outbreak of the First World War and the decision of the Ottoman Empire to join the war on the side of the Central Powers, on 5 November 1914 the British Empire formally annexed Cyprus and declared the Ottoman Khedivate of Egypt and Sudan a Sultanate and British protectorate.