In 1968, Josef Koudelka was a 30-year-old acclaimed theatre photographer who had never made pictures of a news event. That all changed on the night of August 21, when Warsaw Pact tanks invaded the city of Prague, ending the short-lived political liberalization in Czechoslovakia that came to be known as Prague Spring. In the midst of the turmoil of the Soviet-led invasion, he took a series of photographs which were miraculously smuggled out of the country