Land-based aircraft as well as carrier-launched aircraft fought at sea. In the Atlantic Theater, German and Italian aircraft attacked Allied convoys that were protected by fighter aircraft from Allied airfields as long as convoys were within fighter range. As carriers became available, Allied carrier-launched fighters provided protection in those ocean areas that could not be protected by land-based planes. In the Pacific Theater, Japan's successful expansion was typically achieved by progressively using land-based aircraft to support invasions of new areas that were within striking distance of airbases that they had established on previously conquered areas. For the Allies, land-based aircraft at local airfields contributed significantly to America's defense of Midway Island and Guadalcanal. Naval fighters and bombers that operated from land-based airfields were typically delivered to battle zones by aircraft carriers. In both theaters, carrier-launched aircraft played significant roles in dominating the air, and construction of aircraft carriers received priority.