the Cuban missile crisis led to the hotline being set up. and after that, the two nations, US and USSR, decided to set up SALT Treaties, which turned out quite bad, also with the Olympics issue. This led to a halt in the détente process where both nations were at agreement. However, the Berlin Wall collapsed and its problems were solved. Then, the Soviets lost power as the Berlin Wall was set up by them in 1959(?). So the barrier was put down = ending most conflicts between the two countries. this then reduced the power of USSR, due to Mikhail Gorbachev's rule (premier of USSR), ending with the collapse of Soviet Union.
hope it helped!