troops, equipped with Ottoman artillery and machine-guns, for campaigns along the coast against Sollum, Mersa Matruh and Da'aba on the way to Alexandria and from Siwa through the band of oases, Bahariya, Farafra, Dakhla and Kharga, west of the Nile. The Senussi crossed the Libyan–Egyptian border on 21 November 1915 to begin the coastal campaign. Western Frontier Force The Western Frontier Force (WFF, Major-General Alexander Wallace), comprised the 1/6th Royal Scots, 2/7th and 2/8th Middlesex, Territorial infantry battalions, the 15th Sikhs, three cavalry regiments raised from rear details of yeomanry and units of the Australian Light Horse, who fought at Gallipoli as infantry, Royal Naval Air Service (RNAS) armoured cars, the 1/1st Nottinghamshire Royal Horse Artillery (RHA) and two aircraft of 17 Squadron Royal Flying Corps (RFC). Wallace suffered from an old wound and was relieved by Major-General William Peyton and the WFF was reinforced with the 1st South African Brigade (Brigadier-General Henry Lukin) and a detachment of Egyptian engineers on 4 February. The WFF eventually received which made the force capable of advancing a greater distance and the ability to maintain itself in the desert. Coastal campaign On 6 November 1915, sank and the coastguard gun-boat Abbas, and badly damaged Nur el Bahr in the Bay of Sollum. On 14 November, the Senussi attacked Sollum and an Egyptian post was attacked east of Sollum on 20 November. The British withdrew from Sollum to Mersa Matruh, east, which had better facilities for a base and the Western Frontier Force (Major-General Alexander Wallace) was created. On 11 December, a British column at Duwwar Hussein was attacked along the Matruh–Sollum track and in the Affair of Wadi Senba, drove the Senussi out of the wadi. The reconnaissance continued and on 13 December, at Wadi Hasheifiat the British were attacked again and after a delay, forced the Senussi to retreat. The British returned to Matruh until 25 December then made a night advance to surprise the Senussi. At the Affair of Wadi Majid, the Senussi were defeated again but were able to withdraw to the west. Air reconnaissance found more Senussi encampments at Halazin, which was attacked on 23 January in the Affair of Halazin. The Senussi fell back skilfully and then attempted to envelop the British, who were pushed back on the flanks as the centre advanced and defeated the main body of Senussi, who were again able to withdraw. Prelude British