It was activated in 1943 in Algiers, North Africa, to plan the invasion of Sicily. Its main forces for this job were the British 8th Army and the US 5th Army. For some time, it was under command of British Field Marshal Harold Alexander. By mid-1944, though, the small-scale invasion that had been planned earlier blew into a theatre of its own. 15th Army Group had pushed northward through Italy, capturing Rome, and driving the retreating Axis forces into Northern Italy. In December, American Lieutenant General Mark W. Clark became the new commander, and by 1945, they had an unparalleled superiority in Central Europe.