 Since compressed air contains only about 21% oxygen, engineers in Japan developed the Type 93 (nicknamed "Long Lance" postwar) for destroyers and cruisers in the 1930s.It used pure compressed oxygen instead of compressed air and had performance unmatched by any contemporary torpedo in service, through the end of World War II.However, oxygen systems posed a serious danger to any ship that came under attack while still carrying such torpedoes; Japan lost several cruisers partly due to catastrophic secondary explosions of Type 93s.