Background As the 20th century dawned, the U.S. had several interests in the western Pacific to defend; namely, access to the Chinese market and its colonies – the
Philippines and
Guam – which the U.S. had gained as a result of the 1898
Spanish–American War. After Japan's victories in the
Sino-Japanese War and the
Russo-Japanese War, 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. and by Japan's objections to discrimination against Japanese immigrants both in Hawaii and California. As a result, as early as 1897 the
U.S. Navy began to draft war plans against Japan, which were eventually codenamed "
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
Treaty of Versailles gave Japan a mandate over former German colonies in the western Pacific—specifically, the
Mariana,
Marshall, and the
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. Although it envisaged an advance through Micronesia, it called for all the islands in a group to be reduced, rather than for some to be bypassed. The strategy quite reasonably assumed U.S. naval superiority, which the U.S. navy did not possess in the wake of the Japanese
attack on Pearl Harbor. This forced the adoption of a purely defensive strategy.
Rationale and use The leapfrogging strategy was limited by the range of land-based aircraft, unless
aircraft carriers of the
Pacific Fleet could assist. Troops on islands which had been bypassed, such as the major base at
Rabaul, were useless to the Japanese war effort and left to "wither on the vine". General
Douglas MacArthur's
Operation Reckless and
Operation Persecution were successful Allied practices of leapfrogging in terms of landing on lightly guarded beaches and very low casualties but cutting off Japanese troops hundreds of miles away from their supply routes. MacArthur said his version of leapfrogging was different from what he called island hopping, which was the style favored by the
Central Pacific Area commanded by Admiral
Chester W. Nimitz where direct assaults on heavily defended beaches and islands led to massive casualties at
Tarawa,
Saipan,
Guam,
Iwo Jima, and
Okinawa. MacArthur explained his and
William Halsey's strategy: leaflet dropped on Japan depicting the leapfrogging strategy and the increasing Allied dominance in the Pacific theatre
Advantages Leapfrogging allowed the United States forces to reach Japan quickly and not expend the time, manpower, and supplies to capture every Japanese-held island on the way. It gave the Allies the advantage of surprise and kept the Japanese off balance, as they could not defend everywhere in strength.
Disadvantages The bypassed Japanese forces were expected to be ineffective, to "wither on the vine" and starve within a few months, but this did not occur. They cultivated gardens using seeds and equipment imported by aircraft and submarines, worked with local labor, and remained stronger and better-organized than anticipated. They remained capable of offensive action, and mounted major counterattacks against the American forces in the
Battle of Driniumor River and the
Bougainville counterattack. Containing these Japanese forces tied up six American divisions, threatening to make the American Army the one that became strategically ineffective. They did not pursue defeated Japanese forces and engaged in little patrolling beyond their defensive perimeters, allowing the defeated Japanese to regroup and reform. It also left local people at the mercy of the Japanese. When MacArthur
returned to the Philippines, he abandoned leapfrogging in favor of a policy of the complete destruction of the Japanese forces, mainly based on a political imperative of liberating the Filipinos. Australian forces relieved the American garrisons in late 1944 and conducted offensives against the
Japanese on Bougainville and at
Aitape. == Notes ==