In recent years the technical knowledge and experience required of a “capable mariner” have greatly expanded. Not only have navigation, seamanship, and gunnery become much more complicated, but a vast array of the new technical subjects has been added by the application to naval warfare of the products of modern scientific research and by new methods of operation made possible, or made mandatory, by these new additions. World War II, with its scientific and technical developments, particularly in aviation, communications, and electronics, caused the military man to discover a completely new concept of his job. Now we have the A-bomb and the H-bomb, to say nothing of outer space with all that that implies, and research still goes on. The capable mariner of today must have a working knowledge of all these new developments as applied to the art of war at sea.