It was tough to be a German after the second world war. How, given the terrible legacy of Nazism, could you ever feel good about your country again? Well, one answer was to emphasise stories of gallant resistance. And none appeared more gallant than that of Claus von Stauffenberg and the doomed plot to blow up Hitler just a year before the war ended.

On July 20, 1944, Stauffenberg, an aristocratic officer and decorated war hero, placed a bomb in Hitler's conference room at the Wolf's Lair in East Prussia. He then hurried away on a plane to Berlin, intending to help orchestrate the revolution that would follow the death of the Führer. But the Führer did not die. Although the bomb went off, the blast was partly absorbed by the thick conference table and the wooden walls of the meeting room. Hitler staggered out with only superficial injuries.

Not surprisingly, vengeance was swift and brutal. Several hundred people implicated in the plot were executed - including Stauffenberg. Just before he was shot, he cried out: “Long live holy Germany!”

Now Hollywood has decided this is a story worthy of the blockbuster treatment: a feature film starring Tom Cruise as Stauffenberg is being released later this month. But the trouble is, as each of these three books demonstrates, the history of German resistance to the Nazis is not quite as straightforward as a movie-maker might like.

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In Valkyrie, Philipp von Boeselager writes not just about his own somewhat tangential role in the Stauffenberg plot but also about an earlier attempt to assassinate the Führer in 1943. This one failed when the detonator on a bomb on Hitler's plane didn't ignite.

But Boeselager doesn't add much to previous accounts and his own perspective as one of the plotters is strangely muted. That's no doubt partly because the book was compiled more than 60 years after the events it describes (and just before Boeselager died in 2008), but also because of a more worrying problem - what Boeselager chooses to omit. And what he leaves out is any information that might make him or his friends look bad.

As an officer in the German army during the 1930s, Boeselager says that he was part of a group that was “entirely devoted to our military training and, since we lived in barracks far from the cities and were cut off from the press, we were not well informed”. To which one can only reply: “Come off it.” This was a period when the Nazis were openly reshaping society, marginalising and persecuting Jews, and pursuing an aggressive policy of rearmament. And though even Boeselager has to admit that the violent attack on the Jews on Kristallnacht in November 1938 “did not escape our attention”, his attempts to explain why this horror made little difference to him and his comrades are almost risible: “Sports were far more important than political discussion” is one of the lamest of his excuses.

He admits that his father joined the Nazi party in 1934, but only because “he had allowed himself to be persuaded by people from the village”. An explanation that reminds me of the reason one old Nazi gave me for his enthusiastic membership of the Hitler Youth. “It's simple,” he said. “I only joined because I really liked camping.”

There is, of course, a less flattering interpretation of Boeselager's story - which is that though, no doubt, knowledge of the wartime atrocities committed by the Nazis played a part in the decision to kill Hitler, the fundamental reason why Boeselager and his comrades wanted the Führer dead in 1943 was because Germany was losing the war. Pragmatism was more important than principle.

The sense of moral murkiness in Valkyrie is reinforced by the examination of Germans Against Hitler, written by Hans Mommsen, that grand old man of German academia. In this collection of disparate scholarly essays on the resistance movement, Mommsen demonstrates that many of those involved in the attempt on Hitler's life had decidedly dodgy pasts. Or as he says: “We have no alternative but to admit that a considerable number of those who played an active part in the July plot, and in many cases lost their lives as a result, had previously participated in the war of racial extermination, or had at least approved of it for quite a time, and in some cases actively supported it.”

In addition, whatever plans the plotters had for a Germany post-Hitler, they certainly didn't include a return to democracy. If they had managed to kill the Führer, then most likely one antilibertarian regime - albeit a less repressive one - would have succeeded another.

As for Mommsen's book, despite the subtitle, The Stauffenberg Plot and Resistance Under the Third Reich, any buyer should remember that it is not a narrative history of the July 1944 plot. It is a collection of analytical essays designed, primarily, for an academic audience.

Happily, though, there is a book that is perfect for those whose interest in the subject is awakened by the Cruise film. Ian Kershaw's short history is taken directly from the second volume of his magnum opus on Hitler. And this extract, freed from the huge biographical tome, is revealed as a jewel of historical narrative.

Kershaw takes us skilfully through the pre-history of the Stauffenberg plot - from the attempt by the “Swabian joiner” Georg Elser to blow up Hitler in November 1939, to RudolfChristoph Freiherr von Gersdorff's dark, almost comic crack at assassinating the Führer in 1943. Gersdorff, an army intelligence officer, had strapped a bomb to himself (to be detonated by a timing device) and activated it when Hitler arrived at an exhibition of “captured Soviet war booty”. But Hitler “raced through the exhibition”, leaving Gersdorff to dash to the lavatory to defuse the bomb.

Kershaw also pulls no punches when he describes the views held early in the war by the “heroic” Stauffenberg: “He was contemptuous of the Polish people, approved of the colonisation of the country, and was enthusiastic about the German victory. He was still more jubilant after the stunning successes in the western campaign.” You don't need to be a fortune teller to predict that those sentiments won't appear in the film.

Even though Kershaw demonstrates that Stauffenberg was later appalled by the “mounting barbarity” of the Nazi regime, this is clearly not a Hollywood story of “white hats and black hats”. Everyone's hat here is decidedly grey.

Valkyrie by Philipp von Boeselager
Weidenfeld £9.99 pp200
Germans Against Hitler by Hans Mommsen
IB Tauris £12.99 pp326
Luck of the Devil by Ian Kershaw
Penguin £7.99 pp176

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