Yalta Conference (February 4, 1945)

Wartime leaders Franklin Roosevelt, Winston Churchill, and Joseph Stalin meet in Yalta, the Crimea to discuss post-WWII Europe.

Churchill's "Iron Curtain" Speech (March 5, 1946)

Winston Churchill speaks at Fulton about the pressing issue of the encroaching Soviet Union or "iron curtain."

Marshall Plan (June, 1947)

Truman announces that he will carry out George C. Marshall's plan to revitalize the economies of Europe.

Containment Policy (July, 1947)

George F. Kennan publishes his Article X in which he defines American Containment policy towards Russia, which includes firm, but not outwardly aggressive measures to prevent communism from spreading. 
Article X: http://www.historyguide.org/europe/kennan.html

Berlin Airlift (1948-1949)

President Harry Truman reacts diplomatically to Stalin's blockade on Berlin by sending supplies into West Berlin.

Castro Takes Power (1959)

Fidel Castro overthrows Batista and rises to power in Cuba with the help of his rebel guerilla forces.

Korean War (June, 1950 - July, 1953)

Friction between South Korea and communist North Korea eventually leads to war, with support from the Soviet Union on the North side, and support from the U.S. on the South side.