Soviet Union-dominated Warsaw Pact troops invade Czechoslovakia, crushing the Prague Spring; on the same day, Nicolae Ceauşescu, leader of Communist Romania, publicly condemns the Soviet maneuver, encouraging the Romanian population to arm itself against possible Soviet reprisals.

The Soviet Union launches Soyuz 5.

Student Jan Palach dies after setting himself on fire 3 days earlier in Prague's Wenceslas Square to protest the invasion of Czechoslovakia by the Soviet Union in 1968. His funeral turned into another major protest.

Soviet and Chinese forces clash at a border outpost on the Ussuri River.

Venera program: Soviet ''Venera 6'' begins its descent into the atmosphere of Venus, sending back atmospheric data before being crushed by pressure.

Cold War: Negotiators from the Soviet Union and the United States meet in Helsinki to begin SALT I negotiations aimed at limiting the number of strategic weapons on both sides.

The Soviet Tupolev Tu-144 becomes the first commercial transport to exceed Mach 2.

The domestic Soviet Aeroflot Flight 244 is hijacked and diverted to Turkey.

Soviet Union enters ICAO, making Russian the fourth official language of organization.

Luna program: The Soviet Union lands Lunokhod 1 on Mare Imbrium (Sea of Rains) on the Moon. This is the first roving remote-controlled robot to land on another world and is released by the orbiting Luna 17 spacecraft.

Eighty-seven countries, including the US, UK, and USSR, sign the Seabed Treaty outlawing nuclear weapons in international waters.

Mars probe program: ''Mars 2'' is launched by the Soviet Union.

The crew of the Soviet ''Soyuz 11'' spacecraft are killed when their air supply escapes through a faulty valve.

The Soviet Union says it will support the People's Republic of China's admission to the United Nations

The Soviet unmanned spaceship Luna 20 lands on the Moon.

The United States suffers its first loss of an international basketball game in a disputed match against the Soviet Union at Munich, Germany.

A Soviet supersonic Tupolev Tu-144 crashes near Goussainville, France, killing 14, the first crash of a supersonic passenger aircraft.

Soviet Mars 5 space probe launched.

The diplomatic relations between the Soviet Union and Gabon are established.

Soviet Soyuz Programme: ''Soyuz 13'', crewed by cosmonauts Valentin Lebedev and Pyotr Klimuk, is launched from Baikonur in the Soviet Union.

Aleksandr Solzhenitsyn, winner of the Nobel Prize in literature in 1970, is exiled from the Soviet Union.

Portugal and the Soviet Union establish diplomatic relations.

U.S president Richard Nixon visits the U.S.S.R..

Mikhail Baryshnikov defects from the Soviet Union to Canada while on tour with Bolshoi Ballet.

The Soyuz 17 Soviet spacecraft returns to Earth.

The Tupolev Tu-144 goes into service in Soviet Union.

Cold War: Soviet air force pilot Lt. Viktor Belenko lands a MiG-25 jet fighter at Hakodate on the island of Hokkaidō in Japan and requests political asylum in the United States.

Korean Air Flight 902 is shot down by Soviets.

The Soviet Union signs a "friendship treaty" with the Democratic Republic of Afghanistan.

SALT II is signed by the United States and the Soviet Union.

Two Soviet Aeroflot jetliners collide in mid-air over Ukraine, killing 156

Soviet dancer Alexander Godunov defects to the United States.

Soviet Union invades Afghanistan

Miracle on Ice: In Lake Placid, New York, the United States hockey team defeats the Soviet Union hockey team 4-3, in what is considered to be one of the greatest upsets in sports history.

The Soviet submarine ''U 137'' runs aground on the east coast of Sweden.

Cold War: In Geneva, representatives from the United States and the Soviet Union begin to negotiate intermediate-range nuclear weapon reductions in Europe (the meetings ended inconclusively on December 17).

In the Soviet Union, Yuri Andropov becomes the general secretary of the Soviet Communist Party's Central Committee, succeeding Leonid I. Brezhnev.

Lech Wałęsa, the leader of Poland's outlawed Solidarity movement, is released after eleven months of internment near the Soviet border.

American schoolgirl Samantha Smith is invited to visit the Soviet Union by its leader Yuri Andropov after he read her letter in which she expressed fears about nuclear war.

Cold War: Samantha Smith, a U.S. schoolgirl, flies to the Soviet Union at the invitation of Secretary General Yuri Andropov.