The building of a new fleet in the 1960s was made possible with substantial economic support from the United States. During the cold war, the navy was optimized for sea denial in coastal waters to make an invasion from the sea as difficult and costly as possible. With that mission in mind, the Royal Norwegian Navy consisted of a large number of small vessels and up to 15 small diesel-electric submarines. The navy is now replacing those vessels with a smaller number of larger and more capable vessels.