Rear-Admiral Ruitaro Fujita was Commander of 11th Carrier Division attached to 3rd Fleet in1941. He commanded part of Makassar Invasion Force (in Celebes) on 8 February 1942.

He was also a Commander of Seaplane Tender Group, part of Midway Island Invasion Force (2nd Fleet) under command of Vice-Admiral Nobutake Kondo in Operation 'M' (May - June 1942). After that he was promoted to rank of Vice-Admiral and became Commander of Tsingtao Special Base Force, Eastern China in November 1943. He was Commander of South China Fleet by 1945.

He signed surrender of all naval forces in Hong Kong and South China Fleet (together with Major-General U. Okada) to Rear-Admiral Sir Cecil Harcourt, at Government House in Hong Kong on 16 September 1945.