Why do the British and the Americans both agree that the Allies should invade Italy?

The reasons why both the British and the Americans agreed that the Allies should invade Italy was because the British favored a strike against the Axis southern flank that would avoid the strong German defenses in northern France. On the other end, the U. S. Army Chief of Staff General George C. Marshall and the Americans advocated a cross-Channel invasion of France as the shorter road to victory. The United States agreed with the British view that a southern advancement could secure Allied Mediterranean shipping lanes, and provide bombers bases from which to strike Axis southern Europe. They believed that this would drive Italy from the war.