Former British Prime Minister Winston Churchill's "Iron Curtain" speech was first delivered on this date in 1946. The famed speech, given in the unlikely location of Fulton, Missouri, is widely considered a marker of the beginning of the Cold War. In his remarks, Churchill warned of the risks of appearing weak on the world stage or appeasing the Soviet Union, which was hard at work creating satellite states across Europe and Asia to consolidate power within its supposed sphere of influence.
It had been less than a year after the United States, United Kingdom, and the Soviet Union had worked together to defeat Nazi Germany, and things were already heating up between the communist power and the two English-speaking nations. Over the coming decades, the tensions would come to define global politics, with countries on every continent expected to side with the Soviets or the Western group of nations led by the United States. Churchill's remarks clarified that division encouraged a tighter bond between the U.S. and the U.K.
You can read more about the speech at The Guardian, and some excerpts of the speech at the U.K.'s National Archives.