A useful idiot or useful fool is a pejorative description of a person, suggesting that the person thinks they are fighting for a cause without fully comprehending the consequences of their actions, and who does not realize they are being manipulated by the cause's leaders or by other political players. The term was often used during the Cold War to describe non-communists regarded as susceptible to communist propaganda and psychological manipulation. A number of authors attribute this phrase to Vladimir Lenin, but this attribution is not supported by any evidence.
https://en.wikipedia.org/wiki/Useful_idiot