GCSE Modern History/Détente and Refreezing

In the 1970s, tension between the two superpowers relaxed. This period was known as détente.

Why did the Cold War thaw in 1970s?

At the Helsinki conference in 1975 all countries recognized the borders set out at the end of the Second World War (including Germany/Berlin).
The Vietnam War ended.
Nuclear testing damaged the environment and cost a fortune. Anti-nuclear movements supported détente.
The leaders held regular summit meetings.
American astronauts and Soviet cosmonauts shook hands in space.
Both had extremely advanced weapons, and were spending large sums of money to develop them. They realised that this money could be better spent elsewhere.
SALT (Strategic Arms Limitation Treaty) 1 was signed, and progress was being made towards a SALT 2.

The USA boycotted the 1980 Moscow Olympics. In retaliation, the USSR and eastern Europe boycotted the 1984 Los Angeles Olympics.
SALT 2, a USA-USSR agreement to limit nuclear weapons, collapsed because relations between the two countries had deteriorated too far.
There was a revolution in Iran. The new leader was anti-American and anti-Communist, both superpowers were worried.
Jimmy Carter criticised the USSR's suppression of dissidents in the USSR and eastern Europe.
New nuclear weapons were being developed by both the USA and USSR.
There were civil wars in Nicaragua, El Salvador, and Angola where the USA and USSR funded opposing sides.
Ronald Reagan was elected president. He funded the Strategic Defense Initiative ('Star Wars') and took a tougher line on the USSR. He called the USSR the 'Evil Empire' and was more very anti-Communist.
The USSR was fighting for the pro-Soviet government in Afghanistan. The USA was supporting opponents of the government.