50 years ago today, Soviet tanks crushed the Prague Spring. Here are Josef Koudelka's famous photographs of the invasion.

Exactly 50 years ago today, on the night of August 21, 1968, Soviet troops (together with soldiers from several other members of the Warsaw Pact) entered Czechoslovakia and ended the “Prague Spring” — the attempt by Alexander Dubček and other leaders of Czechoslovakia’s Communist Party to put a “human face” on the country’s pro-Soviet regime. That day, a 30-year-old Czech man named Josef Koudelka was in Prague, having decided to put his engineering career on hold for a year and devote himself to photography. With no experience as a journalist, Koudelka took pictures that day that came to symbolize Soviet aggression. The negatives were quickly smuggled abroad and published in New York (without his name, for his own protection). A year later, Koudelka was awarded one of the world’s most prestigious photography honors: the Robert Capa Gold Medal for best published photographic reporting from abroad requiring exceptional courage and enterprise, and in 1971 he joined the Magnum Photos international photographic cooperative, founded by Capa and Henri Cartier-Bresson. Meduza is republishing Koudelka’s photos from Prague, when Soviet tanks arrived 50 years ago today.