I really want to avoid coming across as an armchair general, but the process of bombarding an island from the sea and then sending in an amphibious assault seems wasteful to me.
For example, when the US wanted to capture the Japanese airfield on Pelelui, from what I understand they bombarded the island for about three days, and then sent in Marines who encountered heavy resistance as soon as they hit the beach. The fighting over the next two months resulted in about 8,000 US casualties.
Assuming the US had naval superiority (because they were able to bombard the Island for days), why didn’t they just “besiege” the island. If the US was able to form a naval blockade and prevent the Japanese garrison from being resupplied, wouldn’t they eventually be starved out? Just like what would happen to a besieged city in medieval and ancient warfare? Pelelui doesn’t seem like a very large island, and I’ve heard that the Marines who fought there experienced severe problems due to the lack of fresh water. How long could 10,000 Japanese soldiers expect to maintain a worthwhile defense without any incoming supplies?
I feel like this would be even more so with Iwo Jima, which seems to be essentially nothing more than a volcanic rock with little to no resources.
Wouldn’t this strategy have saved thousands of American lives? I’m assuming the answer is no because it’s not what happened, but I’m curious for the reason why.
If the US was able to form a naval blockade and prevent the Japanese garrison from being resupplied, wouldn’t they eventually be starved out?
Because they did leave some islands to wither on the vine. Most notably, the fleet anchorage at Truk and the base at Rabaul were never subjected to invasions. Air raids, yes (Truk even served as a practice run for some elements of the British Pacific Fleet on 1945 June 14-15), but it's not like every island in the path was subjected to invasion. I commend to your attention the following previous threads:
And we still welcome further contributions from other users, so if you'd like to put in your own oar about island-hopping, please don't let this post stop you!
There are some fantastic answers here, but I would like to add a few points.
Island hopping was the plan for a war with Japan going into WW2. US Navy and Army war planners had been contemplating what a war with Japan would entail since the Russo-Japanese war. Not only had the war planners in the services been contemplating the issue for 35 years, but every senior leader that attended the Naval War College in Rhode Island would spend months planning and war gaming this scenario. The resultant war plan was known as War Plan Orange, and evolved into the Rainbow plans shortly before the war. War Plan Orange was US vs. Japan, while the Rainbow plans included the various allies. War Plan Orange had several different Stages, the first being the establishment of bastions within the Pacific at either Luzon or Guam. It then evolved into the "Through-Ticket" which entailed the US Navy Rushing straight to the Philippines to relieve a besieged US garrison in the Philippines. Finally around 1932, it settled on the island hopping campaign as leaving large land based air forces in their rear became impractical.
The second point is that time was an enemy too. A central tenet of the Japanese war effort was that the American people would not tolerate a long war. Japan underestimated how long the US would be willing to fight the war especially after Pearl Harbor, but there was truth to that belief. There were virtually no consumer goods being manufactured in the US during the war, and inflation was always a danger due to the economic boom. Inflation had been a huge problem in the US during WW1. War bonds were important to help fund the war effort, but equally important is that it took money out of the hands of consumers who suddenly had more spending capital due to the demand for workers, which lowered inflationary pressure. Out of control inflation would have quickly dampened the will of the US to continue the war, and controlling inflation depended on the purchase of war bonds.
Finally, even islands like Iwo Jima would take months to starve out. Many of the other islands were able to be completely self sufficient in regards to food. The 100,000 man garrison at Rabaul as well as another 40,000 in surrounding islands were for the most part, self sufficient for two years from mid 1944 until they were repatriated in 1946. The only shortfalls in food production resulted from being forced into camps by the Australians and having to abandon their fields after the Japanese surrender. The establishment of the camps was deemed necessary as the Australian force of 10,000 was heavily outnumbered, and the Allies were able to provide some additional food to make up for the shortfall. The Allies couldn't take months or years for each new advance into Tarawa, Guadalcanal, New Georgia, Kwajalein, Saipan, Guam, Tinian, Peleliu, the Philippines (or Taiwan,) Okinawa and Iwo Jima as the US public would have tired of the war.
Sources:
Miller, Edward S. War Plan Orange: The US Strategy to Defeat Japan, 1897-1945.
Hiromi, Tanaka Japan in the Pacific War and New Guinea.