Seven decades after the end of World War II, at least one Nazi hunter remains active.For a campaign called Operation Last Chance, Efraim Zuroff, the director of the Israel office of the Simon Wiesenthal Center, arranged for posters featuring a photograph of the Auschwitz-Birkenau concentration camp with a caption reading “Late, but not too late” to appear in major cities in Germany.The 2013 initiative produced tips involving 111 individuals.“You will never have a press conference in which I will say we’re throwing in the towel,” Zuroff maintains. The Nazi war criminals “may be all dead, but I’m not going to announce it.”That said, the era of the Nazi hunters is drawing to a close. To honor them – and ensure that their legacy endures – Andrew Nagorski, who served as Newsweek’s bureau chief in Moscow, Rome, Bonn, Berlin, Warsaw and Hong Kong, and is the author of Hitlerland, has written an account of their efforts, with and often without the authorization of their governments, to track down individuals who instigated and carried out the horrendous crimes of World War II and the Holocaust.Some of Nagorski’s Nazi hunters are more familiar than others. His cast of characters includes Jan Sehn, the Polish judge who handled the interrogation of Rudolf Höss, the longest-serving commandant of Auschwitz; Rafi Eitan, the Mossad agent in charge of the commando unit that kidnapped Adolf Eichmann in Buenos Aires; Fritz Bauer, the prosecutor and judge who orchestrated the Auschwitz trials in Frankfurt in the 1960s; Beate Klarsfeld, who slapped West German chancellor Kurt Kiesinger (a former member of the Nazi Party) and, with her husband, Serge Klarsfeld, traced Klaus Barbie, “the Butcher of Lyon,” to Bolivia, and succeeded in getting him tried in France; Eli Rosenbaum, the director of the Office of Special Investigations in the US Justice Department, which extradited, deported or otherwise expelled 67 Nazi criminals; and Simon Wiesenthal, who called attention to “unprosecuted, unpursued” Nazis during the early days of the Cold War.Nazi hunters did not always agree with one another on tactics. Nor did they always like the men and women they viewed (alas) as rivals. But, Nagorski indicates, they were as one in their implacable determination and their conviction that Nazis should be tried and punished not only to avenge their victims but to educate society by amassing a record of the atrocities of the Third Reich and “establishing the principle that the perpetrators bore direct responsibility for those crimes, whatever they understood those orders to be.” The Nazi hunters, Nagorski reminds us, faced a daunting task. Preoccupied with winning the Cold War against the Soviet Union in the 1940s, ’50s and ’60s, the United States, England and France prosecuted some Nazis but often made exceptions to the rules, as in the case of rocket scientists such as Werner von Braun, who emigrated to the United States. And many West Germans wanted to put de-Nazification behind them, popularizing the term Persilschein (a reference to the laundry detergent Persil) for the widespread whitewashing of reputations. In 1965, Nagorski reports, 57 percent of Germans told pollsters they did not want any more trials of former Nazis.Nagorski understands as well that critics (of the Nuremberg Trials and virtually all subsequent proceedings) have raised concerns about the moral and legal implications of the apprehension, prosecution and punishment of Nazis. Does it matter, they have asked, that the defendants did not violate any laws of the Third Reich? Is the definition of “crimes against humanity” sufficiently clear and compelling? Who has jurisdiction to try these cases? The Nazi Hunters does not provide an in-depth analysis of these issues. Instead, Nagorski indicates that in 2013, in the trial of John Demjanjuk, the German court accepted arguments made decades earlier that defendants could be found guilty as accessories to mass murder if they were “cogs in the machine of extermination” – even if they themselves had not committed an act of violence.He cites, with apparent approval, the claim of Piotr Cywinski, director of the Auschwitz-Birkenau Museum, that this decision was long overdue. According to Cywinski, both the killer and the person standing guard over the prisoners are culpable.“We are in the area not only of law but of morality,” he says. “The bigger moral failure would be to avoid passing judgment.”The Nazi Hunters seems to imply, however, that there is no consensus about the criteria for determining guilt in state-sponsored atrocities and the legal framework in which that determination should be made. Does guilt follow “function” as well as direct participation in crimes? Or, as Serge Klarsfeld maintains, is the notion that guilt attaches to a person’s position “quite Soviet”? In a world that is, alas, awash in crimes against humanity, we have an urgent need to address these complex and controversial questions. Glenn C. Altschuler is the Thomas and Dorothy Litwin professor of American studies at Cornell University.