The Navy's civilian leadership was equally opposed, if for other reasons. On April 3, Mitchell met with Roosevelt and a board of admirals to discuss aviation, and Mitchell urged the development of naval aviation because of the growing obsolescence of the surface fleet. His assurances that the Air Service could develop whatever bomb was needed to sink a battleship, and that a national defense organization of land, sea, and air components was essential and inevitable, were met with cool hostility. Mitchell found his ideas publicly denounced as "pernicious" by Roosevelt. Convinced that within as soon as ten years strategic air bombardment would become a threat to the United States and make the Air Service the nation's first line of defense instead of the Navy, he began to set out to prove that aircraft were capable of sinking ships to reinforce his position.