1950's politicians were Delegate of the Imperial Diet and bureaucrat of the Imperial government before 1945..

For example, see following careers of prime ministers in the 1950's.
Yoshida Shigeru(1948-1954) Before 1945: Diplomat. He tried to peace with Allied powers and was arrested by the order of Tojo.
Hatoyama Ichiro (1954-1956) Before 1945: Delegate of the Imperial Diet. He opposed to the Tojo's cabinet and forced to retirement from 1943 to 1945.
Ishibashi Tanzan (1956-1957) Before 1945: Economist, Journalist, Buddhism priest. He was known as opinion that abandon oversea colonies and progress free trade.
Kishi Nobusuke (1957-1960) Before 1945: Bureaucrat. He was known as neo-bureaucrat to promote controlled economy. He was the Minister of Commerce and Industry of the Tojo's cabinet but in 1944 he changed side to opponents and collapsed Tojo's cabinet.