However , most of the sinkings were carried out by aircraft carrier - based planes , not by land - based bombers as envisioned by Mitchell .
Some of these ships were destroyed by surprise attacks in harbor , others were sunk at sea after vigorous defense .
Most of the sinkings were carried out by aircraft carrier - based planes , not by land - based bombers as envisioned by Mitchell .
Some of these ships were destroyed by surprise attacks in harbor , others were sunk at sea after vigorous defense .