Tlatelolco massacre
Students gunned down ten days before the Olympics

On 2 October 1968 the army and special units opened fire on a student rally in Mexico City's Plaza of the Three Cultures. The government wanted the protests crushed before the Olympic Games opened on 12 October. Officials reported a few dozen dead, but by various estimates as many as 300 to 400 were killed. The truth was suppressed for decades.
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Meanwhile around the world (±25 years)
Whole world
- 1945 Founding of the United Nations — 23 years earlier
- 1947–1991 Cold War — 21 years earlier
- 1948 Universal Declaration of Human Rights — 20 years earlier
- 1949 Founding of NATO — 19 years earlier
- 1980 Smallpox declared eradicated — 12 years later
Europe
- 1953 Discovery of the DNA double helix — 15 years earlier
- 1961 Berlin Wall built — 7 years earlier
- 1968 May 1968 in France — same year
- 1989 Invention of the World Wide Web — 21 years later
- 1989 Fall of the Berlin Wall — 21 years later
Eastern Europe & Russia
- 1945 German surrender and Victory Day — 23 years earlier
- 1957 Sputnik 1, the first satellite — 11 years earlier
- 1961 Gagarin's flight — 7 years earlier
- 1985–1991 Perestroika — 17 years later
- 1989 Revolutions of 1989 — 21 years later
Middle East
- 1948 Founding of the State of Israel — 20 years earlier
- 1979 Iranian Revolution — 11 years later
- 1980–1988 Iran–Iraq War — 12 years later
- 1990–1991 Gulf War — 22 years later
Africa
- 1960 Year of Africa — 8 years earlier
- 1963 The Organisation of African Unity is founded — 5 years earlier
- 1967 First human heart transplant — 1 year earlier
- 1967–1970 Nigerian Civil War and Biafra — 1 year earlier
- 1974 Lucy is discovered — 6 years later
Asia
- 1945 Atomic bombing of Hiroshima — 23 years earlier
- 1953 First ascent of Everest — 15 years earlier
- 1970 Bhola cyclone — 2 years later
- 1971–1971 Bangladesh Liberation War — 3 years later
- 1975–1979 The Khmer Rouge and the Cambodian genocide — 7 years later
Oceania
- 1954 The Castle Bravo test at Bikini — 14 years earlier
- 1959 The Antarctic Treaty — 9 years earlier
- 1992 The Mabo decision — 24 years later
Alive at the time
- Pablo Picasso (aged 87)
- Charlie Chaplin (aged 79)
- Mao Zedong (aged 75)
- Nelson Mandela (aged 50)
- Martin Luther King Jr. (aged 39)
- Neil Armstrong (aged 38)
- Yuri Gagarin (aged 34)
- Harry S. Truman (aged 84)
- Ho Chi Minh (aged 78)
- Dwight D. Eisenhower (aged 78)