The campaign in South Arabia during World War I was a minor struggle for control of the port city of Aden, an important way station for ships on their way from Asia to the Suez Canal. The British Empire declared war on the Ottoman Empire on 5 November 1914, and the Ottomans responded with their own declaration on 11 November. From the beginning, the Ottomans had planned an invasion of Britain's Aden Protectorate in cooperation with the local Arab tribes. The Ottomans had gathered in some strength on the Cheikh Saïd, a peninsula which juts out into the Red Sea towards the island of Perim.