 Complete the following phrase:  The United States had air superiority though many aircraft were lost to surface-to-air missiles and anti-aircraft artillery. U.S. airpower was credited with breaking the siege of Khe Sanh and blunting the 1972 Easter Offensive against South Vietnam. At sea, the U.S. Navy had the run of the coastline, using aircraft carriers as platforms for offshore strikes and other naval vessels for offshore artillery support. Offshore naval fire played a pivotal role in the 