The US dropped the atomic bombs on Hiroshima and Nagasaki in order to end the war more quickly and without so much bloodshed. The fighting, as the US got closer to Japan was so bloody that it made American planners believe that something like one million American troops would be killed or wounded in an invasion of Japan.
The Iron Curtain specifically refers to the imaginary line dividing Europe between Soviet influence and Western influence, and symbolizes efforts by the Soviet Union to block itself and its satellite states from open contact with the West and non-Soviet-controlled areas.
