ABSTRACT
Sonar The submarine’s success in World War I prompted all the major naval powers to develop antisubma rine detection devices. The earliest of the detection devices was the hydrophone, an underwater listen ing device installed below a ship’s waterline. Un fortunately, although the hydrophone gave the direction to the submarine’s location, it could not determine range. Only an active echo-ranging sys tem could provide that, and every major fleet ex cept that of the Soviet Union pursued the devel opment of such a system during the interwar period. By 1937, all but the Soviet and Italian Navies had working echo-ranging sound equip ment. The antisubmarine capabilities of those two navies suffered accordingly.
