On arrival in Cairo, Dempsey found his corps HQ in reserve because the long lines of communication to Eighth Army's spearhead could only sustain two corps (Horrock's X Corps and Lieutenant-General Oliver Leese's XXX Corps). He was therefore employed in the planning of the Allied invasion of Sicily. The overall plan was developed by a Algiers known as Force 141, under Major-General Charles Gairdner. Dempsey temporarily assumed the role of chief of staff of Force 545, the staff responsible for planning the British Eighth Army's part in the operation, until Major-General Francis de Guingand, the Eighth Army chief of staff, could be spared to take over. Dempsey did not like the plan, which involved separate, dispersed landings. He took his objections to Montgomery on 13 March 1943, and then to Gairdner five days later. De Guingand took over on 17 April, enabling Dempsey to return to command of XIII Corps. He discussed the plan with Dempsey, and prepared an appreciation for Montgomery. Montgomery cabled his objections to General Harold Alexander, the 15th Army Group commander, on 24 April. After some debate, the Supreme Allied Commander, General Dwight D. Eisenhower accepted Montgomery's revised plan on 3 May.