The U.S. realizes that japan is a bigger threat than first anticipated so they decide they need to push them back into their homeland.
us troops encounter diseases they have never had to deal with before such as malaria.
After fighting the Japanese for 6 months, the U.S. had trouble finding them as Japanese troops retreated into the thick jungle and hid. In response the U.S. created a blockade around the island to prevent supplies and reinforcements from reaching the Japanese.
when the Japanese finally surrendered the U.S. gained control of very critically important airways, which could be used to more effectively island hop to take out Japanese controlled islands.
After starting to capture more Japanese islands the U.S. pushed japan back to their homeland.