It’s enough to make an old man cry. Just days before publication of his long-awaited autobiography entitled Peeling the Onion, Günter Grass, bleeding heart icon of the German left, has confessed he was once a member of the Nazi SS.

The revelation by the Nobel prize winner, now approaching his 80th birthday, has shocked Germany’s literary and cultural world. It was Grass first and foremost who insisted the Germans “come clean” about their history and that his own generation should not try to pose as “victims” of Hitler’s National Socialist ideology.

Now the great advocate of facing unpalatable truths has lived up to his own standards, but a little late. The revelation came in an interview with Germany’s respected conservative Frankfurter Allgemeine Zeitung (FAZ), and while it is certain to boost interest in his forthcoming autobiography it has done immeasurable harm to the writer’s squeaky-clean reputation.

Grass now says that, although he had told the truth to his wife, those he deceived included his own children and his biographer Michael Jürgs, with whom he spent countless hours apparently going over the minutiae of his life in the latter years of the Third Reich. Jürgs told The Sunday Times yesterday: “I’m deeply disappointed. If he had come clean earlier and said he was in the SS at 17 no one would have cared, but now it puts in doubt from a moral point of view anything he has ever told us.”

It had long been known that Grass, who was only 18 when the war ended, had served in the armed forces and been wounded. But until now he had gone along with the story that he had been drafted into an anti-aircraft unit in his native Danzig. The truth, he now admits, is that he volunteered to join the U-boat fleet, “which was every bit as crazy”, but was turned down and drafted instead into the 10th SS Panzer Division “Frundsberg”, part of the Waffen SS.

“By that stage,” he insists, “the SS were taking anybody they could lay their hands on.” He escaped lifelong identification as an SS member only because by late 1944 the regiments were no longer organised to carry out the customary process of tattooing conscripts’ blood group on their arms.

Grass has not exactly tried to justify his long silence about his experience in the war, but given the rather lame explanation: “My silence all these years was one of the reasons I had to write this book. In the end it simply had to come out.”

But he has not got off lightly. In a separate commentary the FAZ lashed out at him for hypocrisy, recalling in particular his outspoken and now sanctimonious-sounding condemnation of the 1985 visit by Chancellor Helmut Kohl and President Ronald Reagan to Bitburg cemetery where not only American soldiers but also Waffen SS men were buried. “Wouldn’t the debate have been more honest if we had known that one of those blind followers of the SS had grown up to be, like him, a famous champion of freedom and democracy? “We’re not talking about guilt or crimes here. Grass was still little more than a child,” the FAZ added, noting that at least the great author never pretended to have been part of the anti-Nazi resistance and admitted that he believed in Hitler right up until the Nuremberg war crimes trials.

But Grass has hidden behind his wall of silence in the post-war discussion when he could have made a crucial contribution by admitting the truth. Notably he was silent when another former Waffen SS man, Franz Schönhuber, now leader of the far-right Republikaner party, published his autobiography Ich War Dabei (I Was There), which insisted former members of the elite units were unfairly stigmatised.

The debate was heated because Schönhuber made the point that the Waffen SS were exclusively military units, effectively a branch of the regular army, rather than convinced Nazis.

Grass’s belated revelation will mean a complete revaluation of the career of a man who made himself famous for saying the reputation of Germany would forever be linked with the word Auschwitz.

Against that must be set the oblique discussion in his most recent book, Crabwalk, of the possibility increasingly open for discussion, but long and vociferously denied by Grass himself, that Germans were not only perpetrators of Nazi crimes but at least occasionally also victims.

Crabwalk dealt with a Soviet submarine’s sinking of the passenger ship Wilhelm Gustloff in the Baltic in January 1945. When it went down the Gustloff was hopelessly overloaded, primarily with women and children, and its loss remains the worst ever maritime disaster with some 10,000 killed, six times more than the number who died on the Titanic.