Answer:
island hopping or leapfrogging is the term used to describe the allied (mostly US) invasion of Japanese islands in the pacific. The Americans would invade a island far from Japanese mainland and use it as a military base. From there they would invade the next closest island, which was easier since the supply lines weren't extended all the way back to the US. This was done all the way until the US successfully invaded Okinawa, where the US dropped A-bomb on Nagasaki and Hiroshima