Mitchell was concerned that the building of dreadnoughts was taking precious defense dollars away from military aviation. He was convinced that a force of anti-shipping airplanes could defend a coastline with more economy than a combination of coastal guns and naval vessels. A thousand bombers could be built at the same cost as one battleship, and could sink that battleship. Mitchell infuriated the Navy by claiming he could sink ships "under war conditions", and boasted he could prove it if he were permitted to bomb captured German battleships.