Prior to 1906 the Senussi had been a relatively peaceful religious sect of the Sahara Desert, opposed to fanaticism. They then became involved in resistance to the French. In 1911 the Italians invaded Libya, occupying the coast while the Senussi maintained resistance inland and in Cyrenaica. During this period they generally maintained friendly relations with the British in Egypt.
The outbreak of the First World War raised the tension. The Turks made strenuous efforts to persuade the Senussi to attack British occupied Egypt from the west. In the summer of 1915 Turkish envoys, including Nuri Bey, the half brother of Enver Pasha, and Jaafar Pasha, a Baghdadi Arab serving in the Turkish Army. They were eventually successful, convincing the head of the order, Sayyid Ahmed, to begin hostilities against the British with Turkish support.
The original plan was for a three pronged attack on the British. The Senussi would mount attacks along the narrow strip of fertile land on the Egyptian coast, heading towards Alexandria and in the band of oases one hundred miles west of the Nile. At the same time the Emir of Darfur would launch an attack on the Sudan. In the event the three campaigns were fought separately and were defeated in turn.
The coastal campaign began first, in November 1915. The British withdrew from Sollum and Sidi Barrani and concentrated their forces around Mersa Matruh. A Western Frontier Force, under Major-General A. Wallace, was created from the garrison of Egypt, consisting of one cavalry and one infantry brigade, supported by a battery of horse artillery. They were outnumbered by the Senussi, who had 5,000 men quickly trained to fight as regular infantry, supported by a larger number of irregular troops and with a small number of Turkish artillery and machine guns. Despite their advantage of numbers, the Senussi were defeated in encounters at Wadi Senba (11-13 December 1915), Wadi Majid (25 December 1915) and Halazin (23 January 1915).
They were finally defeated at Agagia (26 February), on the coast close to Sollum. The Western Frontier Force had been reinforced by the South African Brigade, under General Lukin. A column under his command was sent west to recapture Sollum, encountering and defeating the Senussi on their way west. Jaafar Pasha was captured during the battle. Sollum was reoccupied on 14 March.
The campaign against the Oases started in February 1916. Sayyid Ahmed occupied the oases at Baharai, Farafra, Dakhla and Kharge, and forced the British to keep a sizable garrison in Upper Egypt while a mobile force was organised to push him back.
In October 1916 a force containing the camel corps and light car units attacked the Senussi positions, forcing them out of Dakhla (17-22 October). Sayyid Ahmed was forced back to his base at Siwa. This British raised a force of armoured cars, and dispatched them to Siwa in February 1917 under the command of Brigadier-General H. W. Hodgeson. This force won an encounter close to Siwa on 3-5 February, forcing Sayyid Ahmed to retreat back into Libya.
His defeat in Egypt fatally undermined Sayyid Ahmed’s position amongst the Senussi. He was soon forced out in favour of his nephew Sayyid Mohammed el Idris, who had opposed the campaign, going into exile in Constantinople. Idris would soon be recognised by the British and Italians as Emir of Cyrenaica, and would eventually become King Idris I of Libya.