A host of new anti-submarine weapons were developed. Forward-throwing anti-submarine mortars were introduced in 1942 to prevent loss of sonar contact. These mortars, the first being Hedgehog, fired a pattern of small depth charges. One type of charge was used to create entire patterns of explosions underwater around a potential enemy, while the second type of round was fitted with contact detonators, meaning the warhead exploded only upon contact with the submarine. A later design enabled a pursuing destroyer or destroyer escort to maintain continual sonar contact 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.