World History/Cold War
A very simple summary: At the end of World War II in 1945, Russia, France, the United Kingdom and the United States divided Germany and Eastern Europe along a line which became known as the Iron Curtain. For 45 years after that, the world lived in fear of Nuclear Holocaust with both sides building more and more missiles.
The Cuban Missile Crisis in the early 1960's was the closest we came to war. The USSR collapsed in the late 1980's due to lack of grain and money. When Russia took the land away from the farmers, they no longer had the will to work.