'Sentinel' was a British tactical deception using dummy equipment and other devices to make it appear that the Nile river delta in northern Egypt was more strongly defended than it actually was (July/September 1942).

Undertaken by Colonel Dudley W. Clarke’s 'A' Force, 'Sentinel' initially relied on the setting out of dummy tanks and the like, but when these were pre-empted for the use of General Sir Claude Auchinleck’s 8^th Army in the area just behind the El Alamein front, Clarke had recourse to an intelligence deception in which leaks suggested that three fictitious British divisions, created for 'Cascade', had arrived to reinforce the 8^th Army and that a real British division, delayed in transit to the 8^th Army, had in fact arrived. The intelligence leaks also sought to convey the impression that the British defence of the Nile river delta was based on a relatively weak forward line based largely on minefields (advertised by warning signs and in the press, and further suggested by the closure of the road linking Cairo and Alexandria) as stronger defences were organised farther to the rear. These stronger defences were simulated for Axis aerial reconnaissance and ground agents by dummy tanks, artillery, motor transport and tented encampments.