Though McCarthy’s “Enemies from Within” is often credited with inaugurating the political movement that bears his name, the second Red Scare was already underway before he made the speech. Red-baiting in politics was not uncommon in the post-war years. Accusing a political opponent of being insufficiently anti-Communist was a frequent tactic used by conservative politicians, and even Harry Truman, a Democrat, used the ploy against his progressive rival Henry Wallace. There was an anti-Communist fervor in American life before the United States entered the Second Cold War, as evidenced in the 1938 formation of the House Committee on Un-American Activities, which primarily investigated alleged Communist activity.

Several months before the end of the war, US President Franklin D. Roosevelt, UK Prime Minister Winston Churchill, and Soviet Premier Joseph Stalin met at the Yalta Conference to discuss the reorganization of Europe in the war’s aftermath. The agreements initially seemed favorable to the United States. Stalin agreed to break the Soviet-Japanese Neutrality Pact and enter the war on the side of the Allies in the Pacific, although it is worth noting that the Soviet Union only declared war on Japan after the atom bombs were dropped on Hiroshima and Nagasaki. Stalin also agreed to maintain peaceful relations with neighboring European countries, but when the war ended, he broke the agreement by invading and occupying much of Eastern Europe.