An aide to Prime Minister Shigeru Yoshida gave internal government information to the U.S. Central Intelligence Agency in the 1950s on Japan's moves to develop a defense capability, a Waseda University professor says.

According to documents found at the U.S. national archives by Tetsuo Arima, a professor of media research, the CIA got the information through former Lt. Gen. Eiichi Tatsumi, who was given the code name "POLESTAR-5."

Tatsumi, who provided Yoshida with expert advice as Japan developed a defense capability following the war, kept the CIA informed on the establishment of government entities such as the Self-Defense Forces and the Cabinet intelligence office.