The Senussi are a Sufi Muslim brotherhood in Libya. They oppose the 1912 invasion of their country by Italy and remain loyal to the Ottoman Sultan in Istanbul. They have maintained a low level insurgency against the Italians but the Turks think they would be better put to work against the British in Egypt. They have sent agents from Turkey to the Senussi, who have supplied them with some modern weapons and have attempted to give them some modicum of military training.
The leader of the Turkish mission to the Senussi is one Nuri Bey, half brother to Ismail Enver, Turkish war minister and paramount leader. He decides that now is the time for the Senussi to show their mettle. He leads them on a raid across the border into Egypt, where they cut telegraph wires and clash with Egyptian troops near Sidi Barrani.
In and of itself the raid is inconsequential, but it worries the British. The political situation in Egypt is uncertain, with the Egyptian army’s loyalty to the recently installed pro-British king uncertain. The fear of the British is that the Senussi will trigger a general uprising by the Egyptians against the British and their collaborators, thereby threatening the Suez Canal, the vital link from Britain to India.
image source (Centenario Prima Guerra Mondiale 1914 – 1918)