What was the strategy to seize key islands to close in on the Japanese mainland called?​

Philippines

Explanation:

on a alt btw

Leapfrogging

Explanation:

Leapfrogging, also known as island hopping, was a military strategy employed by the Allies in the Pacific War against the Empire of Japan and the Axis powers during World War II. The key idea is to bypass heavily fortified enemy islands instead of trying to capture every island in sequence en route to a final target.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.

the name of the theory is landmass theory.