Question

was the iron curtain speech the start of the cold war?

Answer 1

No, it was not.

In 1945, just after World War II, the alliance between the United States, Britain and the USSR ended. An intense rivalry between communist and non-communist nations led to the Cold War.

The Cold War was the result of a clash between communism and capitalism, two opposing world-views. Another cause of the build up to the Cold War was the intransigent attitude of both sides.

Answer 2

Churchill's speech predicted that an Iron Curtain would descend across Europe, it did not cause it to happen.