Détente was a permanent relaxation in international affairs during the Cold War rather than just a temporary relaxation (the so-called "thaw"). Detente is a term usually associated with the relations between America, Russia and China.
The 1970’s witnessed detente. Why?
1) The horrors of Vietnam shocked people.
2) There was a growing fear of a nuclear holocaust especially with the growth in those countries that had nuclear weapons. Also both USA and USSR had huge stockpiles of weapons.
Why did all 3 major powers want to pursue detente ?
China - she was fearful of her isolation in the world. She was also fearful of what USA had done in Vietnam. China’s stockpile of nuclear weapons was a lot smaller than that of USA. China was also worried by her worsening relations with USSR.
USA - she realised that there were better ways of containing communism than the ways that she done in previous years. She was also aware of the massive cost of weapons production and maintaining a huge armed force. A peaceful relationship with the USSR would be very beneficial to USA especially after the cost of the Vietnam War.
USSR - USSR was spending a huge amount on weapons at the expense of basic household goods. Living standards were poor and USSR was also aware that her relationship with China was far from good while USA was trying to improve hers with China.
How did the world's major powers attempt to ease world tension?
USSR and USA:
1963 - hot-line established after Cuban Missile Crisis
1963 - both agreed to only use underground tests for nuclear explosions
1969 - Strategic Arms Limitation Talks (SALT) start
1972 - Richard Nixon, USA president, visited Moscow
1973 - Leonid Brezhnev, USSR leader, visited Washington
1974 - Nixon visited Moscow
1975 - Helsinki Agreement — USA, USSR, Canada + major European powers accept European frontiers set up after World War Two. This recognised that Germany was divided and East European countries agreed to allow their people human rights such as freedom of speech.
China and USA:
USA had backed the Chinese Nationalists in Taiwan since their fall in 1949 and had fought Communist China on behalf of the U.N. in the Korean War. In 1971 a move was made to improve relationships when China invited an American table tennis team to China. Hence the term "ping—pong" diplomacy. USA’s response was to support China’s entry into the U.N., something she had always vetoed. In October 1971, China entered the U.N. Presidents Nixon and Ford both visited China though USA kept a massive naval fleet off of Taiwan. In December 1978, America's President Carter withdrew recognition of Taiwan.
China and Russia:
Relations between these two nations had soured in the late 1950’s over ideological matters. Both communist states accused the other of "revisionism", or moving away from pure communism. Both clashed over their borders and China has always asked for the return of land taken by the USSR in the C19. The territorial issue combined with the ideological issue has done little to ease problems between the two and both tried to develop better relationships with America than the other had.