Excerpt from page 6

.... after Japan's defeat in 1945, Taiwan and the Pescadores were assigned to the Republic of China for purposes of post-war occupation. Taiwan was still under this occupation four years later, when the ROC government fled to Taiwan after the communist victory in the civil war on mainland China.

Sino-Japanese Relations: Issues for U.S. Policy
Congressional Research Service

December 19, 2008
Washington, D.C.

CRS Report for Congress