Winston Churchill's famous "Iron Curtain" speech, given in March of 1946, helped to push the West and the Soviet Union further towards being enemies in the Cold War.
Just a few months before, the US and the USSR had been allies against Germany in WWII. After the war ended, some people (like Churchill) were arguing that the Soviets were a danger and that the West should be vigilant to be sure that the Soviets did not put any more of the world behind their "iron curtain."
This speech by Churchill helped to make Americans feel that the Soviets were a danger. It also helped make the Soviets angry at the West. By doing these things, it raised tensions between the two sides and helped to get the Cold War going.