The Sicily Campaign also marked the first time in World War II that a complete U.S. field army had fought as a unit. With over 200,000 men in its ranks by the time it reached Messina, the American Seventh Army employed the services of more than 150 different types of units, from infantry regiments to graves registration companies. The final victory was achieved only through the cooperation and collaboration of thousands of individuals from every branch of service.

Strategically, the Sicilian operation achieved the goals set out for it by Allied planners at Casablanca. Axis air and naval forces were driven from their island bastion and the Mediterranean sea lanes were opened to Allied commerce. Hitler had been forced to transfer troops to Sicily and Italy from other theaters, and Mussolini had been toppled from power, thereby opening the way for the eventual dissolution of the Rome-Berlin Axis and Italy's ultimate surrender. Although U.S. military leaders had not initially planned to use Sicily as a springboard for an invasion of Italy, the impact of the operation on the tottering Fascist regime begged exploitation, and the Allies quickly followed up their victory by invading Italy in September 1943.

Yet for all its achievements, the Sicily Campaign also demonstrated some weaknesses in Allied capabilities, particularly in the realm of joint operations. None of the Allied commanders had much experience in joint air-land-sea operations, and consequently the three services did not always work together as well as they might have. Ground commanders complained about the lack of close air support and the inaccuracy of airborne drops, air commanders complained of their aircraft's being fired upon by Allied ground and naval forces, and naval officers chided the land commanders for not fully exploiting the fleet's amphibious capabilities to outflank the enemy once the campaign had begun. Similarly, General Alexander's unfortunate decision to broaden the Eighth Army's front at the expense of the Seventh Army can be attributed to the newness of combined operations, for the decision reflected the British Army's proclivity to underestimate American military capabilities�an attitude that American G.I.s proved unjustified during the Sicily Campaign.