After three unsuccessful attempts to break the Gustav Line, British General Sir Harold Alexander, Commander-in-Chief (C-in-C) of the Allied Armies in Italy (AAI, later designated 15th Army Group), decided to make a coordinated attack with both the U.S. Fifth Army and Lieutenant General Sir Oliver Leese's British Eighth Army, codenamed Operation Diadem. As was the British custom, General Alexander gave his subordinates considerable latitude in how they went about implementing his orders. This allowed Juin to put forward a major modification to the plan. He proposed that the CEF, now increased to four divisions, advance through the rugged Aurunci Mountains and outflank the German positions. He was aware of the difficulty of trying to advance, much less exploit a breakthrough over the mountain trails, but felt that the and Moroccan Goumiers could do it.