until a definite "hit" was achieved. Additionally, new weapons were designed for use by aircraft, rapidly increasing their importance in fighting submarines. The development of the FIDO (Mk 24 mine) anti-submarine homing torpedo in 1943 (which could be dropped from aircraft) was a significant contributor to the rising number of German sub sinkings. Pacific Theater Japan, the United States, Great Britain, The Netherlands, and Australia all employed anti-submarine forces in the Pacific Theater during World War II. Because the Japanese Navy tended to utilize its submarines against capital ships such as cruisers, battleships and aircraft carriers, U.S. and Allied anti-submarine efforts concentrated their work in support of fleet defense. Early Japanese submarines were not very maneuverable under water, could not dive very deep, and lacked radar. Later in the war, Japanese submarines were fitted with radar scanning equipment for improved hunting while surfaced. However, these radar-equipped submarines were in some instances sunk due to the ability of U.S. radar receivers to detect their tell-tale scanning emissions. For example, sank three Japanese radar-equipped submarines in the span of four days. In 1944, U.S. anti-submarine forces began to employ the FIDO (Mk 24 mine) air-dropped homing torpedo against submerged Japanese subs with considerable success. In contrast, Allied submarines were largely committed against Japanese merchant shipping. As a consequence, Japanese anti-submarine forces were forced to spread their efforts to defend the entirety of their merchant shipping lanes, not only to resupply their forces, but also to continue the necessary importation of war material to the Japanese home islands. At first, Japanese anti-submarine defenses proved less than effective against U.S. submarines. Japanese sub detection gear was not as advanced as that of some other nations. The primary Japanese anti-submarine weapon for most of WWII was the depth charge, and Japanese depth charge attacks by its surface forces initially proved fairly unsuccessful against U.S. fleet submarines. Unless caught in shallow water, a U.S. submarine commander could normally dive to a deeper depth in order to escape destruction, sometimes using temperature gradient barriers to escape pursuit. Additionally, during the first part of the war, the Japanese tended to set their depth charges too shallow, unaware that U.S. submarines possessed the ability to dive beyond 150 feet. Unfortunately, the deficiencies of Japanese depth-charge tactics were revealed in a June 1943 press conference held by U.S. Congressman Andrew J. May, a member of the House Military Affairs Committee