In 1955, the United States was entering the final stages of McCarthyism or the Second Red Scare. During this low point in American history, the US government looked high and low for Communist spies.
. . .
In 1955, the U.S. First Army Headquarters prepared a manual called How to Spot a Communist. Later published in popular American magazines, the propaganda piece warned readers, “there is no fool-proof system in spotting a Communist.” “U.S. Communists come from all walks of life, profess all faiths, and exercise all trades and professions. In addition, the Communist Party, USA, has made concerted efforts to go underground for the purpose of infiltration.” And yet the pamphlet adds, letting readers breathe a sigh of relief, “there are, fortunately, indications that may give him away. These indications are often subtle but always present, for the Communist, by reason of his “faith” must act and talk along certain lines.” In short, you’ll know a Communist not by how he walks, but how he talks.
Via Mary Daniels Brown