The Allies captured bases that helped the next advance and cut off other Japanese positions. They did not need to storm each island to reduce its military value.
Japan's empire covered widely scattered islands and long sea routes. At Midway in June 1942, the loss of important aircraft carriers, ships that carry and launch aircraft, weakened Japan's naval air power. As Allied air and naval strength grew, the Allies could increasingly choose where to concentrate attacks instead of fighting for each defended island.
Island hopping meant capturing useful bases and bypassing or isolating others. A base provided airfields, ports and facilities from which forces could operate. Capturing one could bring the next target within reach of aircraft and ships. In 1944, bases in the Marianas, an island group in the Pacific, brought long-range bombers close enough to strike Japan more regularly.
A garrison is a force stationed to defend a place. A Japanese garrison left on an island might still hold that territory, but if cut off from supplies and the main Allied route, it could do little to stop the advance. Bypassing it could avoid the cost of a direct assault. The selected bases still needed supply ships, and some of the landings the Allies chose were extremely costly.
Worked example: Does holding an island mean it can stop the advance?
An isolated Japanese garrison remains on its island while Allied forces move past it.
- Ask whether its troops can obtain supplies or threaten the route the Allies are using.
- If they are cut off, they may hold the island without being able to reinforce other positions or block the advance.
- The Allies can then use forces elsewhere instead of paying the cost of capturing that particular island.
Watch out for this
Island hopping meant attacking every island in order.
The strategy selected useful positions and bypassed or neutralised others. Selection was its main advantage.
Check your understanding
Why were bases in the Marianas useful to the Allied advance?
- They mattered mainly because increasing the number of occupied islands was the aim of the strategy.
- They brought aircraft closer to Japan and provided positions from which to support further operations.
- Once captured, they removed the need to keep bringing fuel and equipment across the Pacific.