On August 19, 1968, Josef Koudelka, a 30-year-old aviation engineer, returned to his home in Prague from Romania, where he had gone to take pictures of Gypsies. The next night Koudelka was awakened by a friend calling to say that Soviet tanks were in the streets. Koudelka, who had never done any journalistic work, sped out to spend most of the next seven days compiling an extraordinary record of the surprise attack that Leonid Brezhnev launched to crush the reforms of Alexander Dubcek’s “Prague Spring,” and the responses of his brokenhearted countrymen. As 165,000 invading troops and 4,600 tanks quickly took control of Czechoslovakia, a country of 12 million, and as paratroopers seized Dubcek and flew him out for coercive talks in Moscow, Koudelka raced around his hometown capturing something more than an excellent historical record. The 250 photographs in this book constitute a rare and poetic vision of a nation coming together, not in victory but in defeat. The images of young people sitting in front tanks, or boys strutting with their flag, certainly convey widespread defiance, anger, betrayal, and bits of commendable bravura. But even more compelling are Koudelka’s pictures showing the private expressions of fear of citizens as they reflexively draw their fists to their cheeks or gape in open-mouthed horror or simply stand in stoop-shouldered but unmistakably sullen submission as the Soviets direct traffic. Koudelka took his photos as his own gesture of personal resistance. For some time he kept them hidden. After a year some made their way to the West, where Magnum Photos distributed them, crediting them to an unknown person referred to as PP, for Prague Photographer. Koudelka kept his role secret for another 16 years, to protect his Prague relatives from possible reprisals by Dubcek’s hard-line successors. Now on the 40th anniversary of the invasion, the Aperture Foundation has published this powerful album and is sponsoring an exhibition at its gallery in New York that runs through Oct. 30th.