The German and American submarine campaigns against their opponents' merchant shipping demonstrated the need for an anti-submarine warfare strategy. While the Allies took extensive measures to combat the threat of German U-boats, the Japanese failed to effectively counter the American submarines which ultimately choked Japan's industrial production and paralyzed her navy. Japan also notably failed to institute an anti-commerce campaign where systematic use of commerce raiders could have made Allied operations much more complex and conquering and holding Japanese-held islands more difficult. American war planners failed to appreciate that technological advances in submarines and naval aviation had made Mahan's doctrine obsolete and did not anticipate a preemptive strike from the Japanese. In particular, they did not yet know either that aircraft would be able to effectively sink battleships or that Japan might put the American battleship force (the Battle Line) out of action at a stroke, which actually happened at Pearl Harbor on December 7, 1941. American plans changed after this attack. Even after major Japanese defeats like Midway, once the effectiveness of aircraft carriers was known, the Americans favored a methodical "island-hopping" advance, never going far beyond land-based air cover. Meanwhile, a blockade was imposed from the very beginning of the war, with the first American submarine, , arriving off Japan on about 31 December 1941. A number of requirements grew out of Orange, including the specification for a fleet submarine with high speed, long range, and heavy torpedo armament. These coalesced in the submarine in 1932 (only to be rejected and returned to with the in around August 1941). The demand for submarines of this size also drove the development of the notoriously problematic Mark 14 torpedo (and its equally notorious Mark VI exploder), under the guidance of Commander Ralph W. Christie. The Navy also spent "several hundred thousand dollars" to develop powerful, compact diesel engines, among them the troublesome Hooven-Owens-Rentschler (HOR), which proved useful for railroads. See also How Japan Plans to Win, by Kinoaki Matsuo (1942) Plan Dog memo Singapore Strategy United States color-coded war plans References Further reading Imperial Japanese Navy Japan–United States military relations Military doctrines Military history of the United States during World War II United States color-coded war plans United States Navy in the 20th century pt:Plano de guerra vermelho#Plano de guerra conjunto vermelho-laranja