The term was invented by Mao Zedong. It’s hard for me to believe that the term was in use in American English in 1945.
Mao picked that up from the International Communist movement. The phrase was in use among American Communists, but it does sound strange fot Truman to use it in the same way people use it now.
US leftists used the phrase in the 70s, many influenced by Mao, others by their own leftist parents’ use of the phrase. Some used it seriously, others ironically.