Answer:
1. Germany invades poland Sept. 25th 1941
2. France falls to German forces June 22nd 1940
3. Battle of britain. Jul, 10th 1940
4. Japan bombs pearl harbor nov, 25th 1941
It's called condensation.
The Iron Curtain was a problem because it blockaded access to East Berlin and prevented the free flow of Germans across the borders between East and West Germany. More broadly it prevented the movement of ideas and peoples across this artificially created boundary. And more importantly than that it signified the dividing line of the Cold War between Western Europe and the United States and the Soviet Union which had a major impact on fomenting mistrust and conflict.
I don't know search on Google
