By the 1930s, in addition to the puppet state of Manchukuo, Japanese colonial rule extended to Taiwan, Korea, the Southern Sakhalin Islands, the Kwantung Territory of Manchuria‘s Liaodong Peninsula, and the South Sea Mandate consisting of the Marshall, Caroline, Mariana and Palau Islands.

Follow this link to get a better picture of many WWII battles to be fought in the South Sea Mandate: U.S. Army Western Pacific Campaign