Book excerpt: The modem U.S. Navy has been built around the aircraft carrier. That ship, with its battle group of surface ships and submarines and its resupply vessels, has been the major tool for projecting power ashore and controlling the seas during wartime. In peacetime, the carrier battle group has been used to remind national leaders of U.S. power through its presence in areas of tension. Such presence, according to its proponents, has deterred aggression, reassured allies, and allowed a more rapid response to regional crises than if carriers had sailed from the United States. The average aircraft carrier, however, spends less than a quarter of its life providing presence--that is, being 'on-station'--in overseas theaters. The main constraint on getting more presence out of each carrier is that the Navy limits the amount of time sailors spend at sea. In an environment in which demands for overseas presence are high and financial constraints are great, the Navy may want to get more out of the forces it is paying for. The Congressional Budget Office (CBO) examined several alternatives to improve the efficiency of carrier operations. They range from altering carrier deployment cycles to establishing an overseas home port for a carrier on the Mediterranean Sea.