The Dies Committee—later known as the House Un-American Activities Committee—is formed to investigate subversive activities within the United States. The committee, headed by Texas Democrat Martin Dies, initially targets Nazi sympathizers but eventually comes to focus almost entirely on the Communist threat.
Congress passes the Smith Act, which makes it illegal to assist any groups "who teach, advocate, or encourage the overthrow or destruction of the government of the United States by force or violence." Hundreds of American Communists will later be charged for violations of the Smith Act.
Franklin Roosevelt, Winston Churchill, and Josef Stalin meet in the Soviet resort town of Yalta to make plans for the postwar era. In a problematic compromise, Roosevelt accedes to Churchill's and Stalin's plans for spheres of influence in Europe even while convincing the British and Soviet leaders to sign on to a statement affirming the principles of democracy.
Franklin Delano Roosevelt dies of cerebral hemorrhage just 82 days into his fourth term, elevating newly installed Vice President Harry S. Truman to the presidency.
Former British Prime Minister Winston Churchill delivers his famous "Iron Curtain" speech at a college in Missouri. "From Stettin in the Baltic to Trieste in the Adriatic," Churchill declares, "an Iron Curtain has descended across the Continent" of Europe.
A coup in Czechoslovakia installs a Communist government, heightening American fears that Communists will seize power in Eastern Europe by any means necessary.
President Harry S. Truman requests congressional funding to support the government of Greece in its civil war against Communist insurgents, couching his request in dramatic rhetoric now known as the Truman Doctrine, which defines Communist victory anywhere in the world as a threat to American security: "Totalitarian regimes imposed on free peoples, by direct or indirect aggression, undermine the foundations of international peace and hence the security of the United States."
President Harry S. Truman issues Executive Order 9835, establishing a Loyalty- Security Program for all federal employees. Designed to pre-empt Republican charges of Communist infiltration of the government, Truman's loyalty oaths only heighten the country's growing fears of Communist subversion.
Congress passes the Taft-Hartley Labor-Management Relations Act over President Truman's veto, sharply curtailing the rights of organized labor while forcing unions to purge Communists from their ranks.
The House Un-American Activities Committee opens hearings investigating Communist activity in Hollywood.
Screenwriter John Howard Lawson, a hostile witness before the House Un-American Activities Committee, refuses to answer, on constitutional grounds, whether he is or was a member of the Communist Party. He is ejected from the hearing and later charged with Contempt of Congress.
The House of Representatives issues citations for Contempt of Congress to the Hollywood Ten—John Howard Lawson, Alvah Bessie, Herbert Biberman, Lester Cole, Edward Dmytryk, Ring Lardner Jr., Albert Maltz, Samuel Ornitz, Adrian Scott, and Dalton Trumbo.
The Motion Picture Association confirms the blacklisting of the Hollywood Ten from employment in the film industry.
Glenn Taylor, Progressive Party candidate for Vice President on Henry Wallace's ticket, is arrested in Alabama for violating segregation laws by attempting to hold an integrated political rally. Taylor's jailor is Birmingham police commissioner Bull Connor, who will later became notorious for unleashing attack dogs on peaceful civil rights protestors associated with Dr. Martin Luther King, Jr.
The Soviets blockade West Berlin, leaving the city—which is surrounded on all sides by Communist East Germany—without access to food and supplies. The Truman administration organizes a military airlift to supply the besieged city. The Berlin Airlift will last for nearly a year, delivering 1.5 million tons of supplies via 200,000 separate flights before the blockade is lifted in May 1949.
The Soviet Union rejects participation in the Marshall Plan, with Stalin's Foreign Minister, V.M. Molotov, calling it an "imperialist" plot to enslave Eastern Europe.
The Democratic Party Convention nominates President Truman to run again as its candidate for president. Northern liberals succeed in including a strong civil rights plank in the party platform, leading to the defection of conservative Southern Democrats to the segregationist States Rights (or Dixiecrat) Party.
Southern Democrats opposed to President Truman and the Democratic Party's liberal position on civil rights convene in Alabama to form the new States Rights Party (better known as Dixiecrats), which nominates South Carolinian Strom Thurmond for president.
President Truman signs Executive Order 9981, ending racial segregation of the armed forces.
Alger Hiss and Whittaker Chambers both testify in a televised hearing of the House Un-American Activities Committee. It is the first time any Congressional hearing has been broadcast over television.
The Berlin airlift ends in victory for the Western Allies as the Soviets lift their blockade on the city.
The Soviet Union successfully detonates its first atomic bomb. The loss of its atomic monopoly comes as a terrible shock to the United States and its people.
Chairman Mao declares victory in the Chinese Civil War, creating the Communist People's Republic of China.
The Congress of Industrial Organizations votes in its national convention to revoke the charter of the United Electrical Workers, the third largest union in the CIO, for failing to purge itself of Communist influence. Ultimately twelve left-leaning unions, and countless individual left-wing organizers, will be booted from the CIO.
Generalissimo Chiang Kai-Shek, longtime American ally and leader of the anticommunist Chinese Nationalists, flees mainland China to organize the Republic of China on the island of Taiwan.
Alger Hiss is convicted for perjury after a jury concludes that he made false statements in denying Whittaker Chambers' allegations that the two men had known each other as Communists in the 1930s. Hiss will serve more than three years in federal prison.
Wisconsin Senator Joseph McCarthy gives a speech in Wheeling, Virginia, dramatically claiming, "I have in my hand a list of 205 cases of individuals who appear to be either card-carrying members or certainly loyal to the Communist Party" within the United States State Department.
Communist North Korean troops invade South Korea, beginning the Korean War
Julius and Ethel Rosenberg are convicted of passing atomic secrets to the Soviet Union.
Soviet Communist leader Josef Stalin dies of a stroke.
The Army-McCarthy hearings begin, broadcast live in their entirety by ABC television.
Army attorney Joseph Welch, disgusted by McCarthy's attacks against his own assistant counsel, asks the senator, "Have you no sense of decency, sir, at long last?"
The United States Senate censures Senator Joseph McCarthy for "conduct contrary to Senatorial tradition."