the Senussi attacked Egypt, which was occupied by the British Empire. The Senussi were persuaded to attack by the Ottoman and German Empires, as part of a strategy to capture the Suez Canal.
One of the campaign's strategies saw the Senussi advance through the Sahara desert, much in the same way as the lost army of Cambyses. The Senussi successfully captured the oasis towns of Baharai, Farafra, Dakhla and Kharge in 1916.
The British Empire forces included British, South African, Australia and New Zealand, and Indian Sikh troops. An interesting account of the Australians in the Senussi battles can be found here, with some great pictures.