Island Hopping was a strategy put in place by the Allies during WWII to defeat Imperial Japan. The strategy consisted of Allied forces bypassing the more heavily defended "fortress" islands and outposts such as Rabaul, but instead securing smaller, less defended yet still important to progress islands. The advantages were apparent, the Allies would expend far less manpower and thus experiences far less losses if they were not forced to occupy every single fortified island in the Pacific.
This was helped largely by the Allied naval and aerial superiority in the area which allowed functioning blockades to be maintained, making the former strongpoints fundamentally useless, "withering on the vine" as many Allied planners put it.
Much of the concept for the eventual Island hopping strategy that was to be employed during the war was descended from Plan Orange, a 1904 plan by the United States for a potential Pacific War against Japan. The most important aspects it outlined were uses of geography in a sense that Japan was an island nation with limited natural resources, therefore it was easily possible to blockade the country and starve it into submission, rendering it impossible for Japan to take any offensive action.
However, being a plan developed even before World War I, it was impossible to foresee every aspect that would need to be examined in the future conflict. Also importantly, developments in the interwar years only further outdated the plans by changing the strategic situation.
For example, following the defeat of Germany in World War I, Japan acquired New Guinea and the Solomon Islands, as well as immediately constructing impressive fortifications/air bases from which to challenge American opposition.In a similar manner to the Americans, Japan had been developing its own planes to maintain ultimate control of the Pacific and end all American opposition.
The first full use of the Island Hopping strategy finally came in early 1943 with Operation Cartwheel, the full attack on the Solomon Islands and New Guinea spread apart into two pincer movements, the more land based New Guinea route commanded by Douglas MacArthur and the more sea-based route through the Solomons commanded by Chester W. Nimitz. The plan worked well, with Allied forces moving through the region quickly and finally capturing most of the strategic sectors by mid 1944. However, quickly following came the shock change of the plane by MacArthur which involved the capturing of the Philippines. This decision was looked down upon for it was known that it would cost exceedingly high casualties for relatively little strategic gain, though the changes were approved. The most common explanation for MacArthurs reasoning was to fulfill his promise from his exile from the Philippines of a return.
However, the campaign continued on as usual with Allied forces continuing to "island hop" around the Pacific, gaining ground ever closer to mainland Japan until finally, Okinawa was reached. At that point, the main priority was securing the remaining sectors that had to be captured and focusing on the bombing campaign on the mainland.
Even isolated Japanese garrisons however did not die off. Oftentimes, the Japanese resorted to farming and fishing of the islands, creating miniature villages while still waiting for any Allied attacks. In all, Island hopping's policy of excluding heavily fortified islands most likely saved many Allied lives, with most isolated troops eventually giving up once they heard of the empire's surrender. However, there were numerous cases of dozens of Japanese troops holding out in caves and jungles for up to sixty years following the war's end.
- Hopkins. B. William. the Pacific War: The Strategy, Politics, and Players that won the War. Zenith Press (2008), Page 6