Opposition to communism. Anti- communism was the defining mark of U.S. foreign policy during the Cold War, which sought to cheque Soviet expansion around the globe. In domestic politics, being seen as "tough on communism" was often a litmus test for American politicians; anything less was to court electoral disaster. Anti-communism reached an extreme during the McCarthy era, in the early 1950s, when Senator Joseph McCarthy led an unscrupulous witch-hunt to root out alleged communist sympathisers in U.S. government service.