Leapfrogging (military)

Leapfrogging, also known as island hopping, was a military strategy employed by the Allies in the Pacific War against Japan and the Axis powers during World War II. The idea was to bypass heavily fortified Japanese positions and instead concentrate the limited Allied resources on strategically important islands that were not well defended but capable of supporting the drive to the main islands of Japan.

By the late 19th century, the U.S. had several interests in the western Pacific to defend; namely, access to the Chinese market, and colonies – the Philippines and Guam – which the U.S. had gained as a result of the Spanish–American War (1898). After Japan's victories in the Sino-Japanese War (1894–95) and in the Russo-Japanese War of 1904, the U.S. began to regard Japan as a potential threat to its interests in the western Pacific. This antagonism was intensified by Japan's objections to an attempt to annex Hawaii to the U.S. (1893) and by Japan's objections to discrimination against Japanese immigrants both in Hawaii (1897) – on this occasion, Japan sent the cruiser Naniwa to Honolulu, Hawaii – and in California (1906, 1913). As a result, the U.S. Navy began to draft, as early as 1897, war plans against Japan, which were eventually code-named "War Plan Orange". The war plan of 1911, which was drafted under Rear Admiral Raymond P. Rodgers, included an island-hopping strategy for approaching Japan.

After World War I, the Versailles Treaty gave Japan a mandate over former German colonies in the western Pacific; specifically, the Mariana, Marshall, and Caroline Islands. If these islands were fortified, Japan could, in principle, deny the U.S. access to its interests in the western Pacific. Therefore, in 1921, Major Earl Hancock Ellis of the U.S. Marine Corps drafted "Plan 712, Advanced Base Operations in Micronesia," a plan for war against Japan which updated War Plan Orange by incorporating modern military technology (submarines, aircraft, etc.) and which again included an island-hopping strategy. Shortly afterwards, a British-American reporter on naval affairs, Hector Charles Bywater, publicized the prospect of a Japanese-American war in his books Seapower in the Pacific (1923) and The Great Pacific War (1925), which detailed an island-hopping strategy. The books were read not only by Americans but by senior officers of the Japanese Imperial Navy, who used "island-hopping" in their successful southeast Asia offensives in 1941 and 1942.

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