In his studio in the Behlendorf woods, near the Baltic city of Lübeck, Günter Grass reflects on the outcry over his fictive memoir Peeling the Onion. His mention, four years ago, of having been drafted as a teenager into the Waffen SS at the tail end of the second world war sparked the most explosive in a half-century of career controversies. "I'm used to it by now," he says. "What I do is sometimes – at least in Germany – met with wounding campaigns. I always face the question: should I grow myself a thick skin and ignore it, or should I let myself be wounded? I've decided to be wounded, since, if I grew a thick skin, there are other things I wouldn't feel any more."
His bestselling debut novel, The Tin Drum (1959), was decried in some quarters as blasphemous pornography, and banned in dictatorships from the Eastern bloc to Iberia, while his novel Too Far Afield (1995) was savaged by critics, not least for raining on the unification parade. The story of his stint in the Waffen SS was broken in the German press in 2006 as a shocking disclosure, though "it came out later that I'd spoken openly about it in the 60s," he says. "Nobody was worked up by it at the time."
That was in an era turning its back on the past amid Germany's "economic miracle", whose amnesia was assailed by Grass and other writers, including Heinrich Böll, Hans Magnus Enzensberger and Martin Walser – before opinion shifted with the Auschwitz trials and 1968 student protests.
Yet for decades, he wrote in Peeling the Onion, he "refused to admit" to the "double letters" of the Waffen SS. He always avowed membership of the Hitler Youth, volunteering without success for the submarine corps at 15, and being conscripted as a tank gunner at 16, before being wounded, never having fired a shot. Yet, as one of the "schoolboy generation" burdened with crimes he learned of only as a PoW in US hands, he wrote: "What I had accepted with the stupid pride of youth I wanted to conceal after the war out of a recurrent sense of shame." That Grass took 60 years to address his Waffen SS membership in his work might be a reminder of the difficulty of the task he undertook. As his oeuvre suggests, the past is never "come to terms" with, but recurs in a perpetual grappling with responsibility and guilt of the kind that "hibernates in dreams".
On whether he might have handled things differently, he says, "I would have had to write my autobiography earlier. It was portrayed . . . as though I'd made a confession – and even that full of false comparisons. I did not volunteer for the Waffen SS, but was, as were thousands of my year group, conscripted. I did not then know as a 17-year-old that it was a criminal unit. I thought it was an elite unit."
For Grass, his conscription has less significance than the unquestioning beliefs of his youth, for which he claims responsibility, and spent a lifetime "working through" in fiction, poetry, drama, essays and memoir. "I belonged to the generation that grew up under National Socialism, and was blinded and led astray – and allowed itself to be led astray," he says. Soon after 1945, "while many were retrospectively counting themselves members of the German resistance, I said: 'No, right until the end, I believed like an idiot in the final victory.' I was shattered when the Germans capitulated. I never made a secret of it. Everything I have done since emerged as an insight after the war."
Though the "Grass affair" brought attacks on his moral authority, he has never styled himself "Germany's conscience" ("No one person can be the conscience of a country – it's stupid"). Accused of hypocrisy in attacking others' wartime records, he objects: "When I criticised [Kurt Georg] Kiesinger because he wanted to be chancellor, I was talking about a man who . . . during the Nazi-era, had a leading position in the propaganda department. He was no 17-year-old."
A lifelong Social Democrat, though no longer a party member ("I criticise them but I'm still on their side"), Grass sees the furore as politically driven. "I was supposed to keep my mouth shut. That didn't work. I still keep opening my mouth."
The controversy is touched on in an exhibition in Günter Grass House, the Lübeck museum that houses prints, watercolours and sculptures by the 1999 Nobel laureate. It was founded in 2002 in the 15th-century print works where he keeps an office, near a red-brick Gothic cathedral like those in Danzig, his Hanseatic birthplace (now Polish Gdansk). "Günter Grass and Poland", on until January 31, has a newly unearthed photograph from his first return in 1958, clasping his Slav great-aunt Anna, a Kashubian in voluminous skirts who inspired the potato-field conception in his most famous novel.
Later he met the Solidarity leader Lech Walesa, who in 2006 demanded that Grass hand back his honorary citizenship of Gdansk. Grass says he wrote to the mayor, and the idea was rejected. "The people of Gdansk said: 'No, he belongs to us!' I'm there every other year; I'm proud they celebrate me." In 2005 he showed 10 translators around the city on the occasion of new 50th-anniversary translations of The Tin Drum. The English one, by Breon Mitchell – out this month in Vintage paperback – is unexpurgated and more faithful, Grass feels, to his "tapeworm-long sentences".
His studio barn is next to the house he shares with his wife Ute, an organist. Downstairs he hammers on his blue Olivetti, and upstairs makes prints. With his "walrus moustache" and pipe paraphernalia, Grass seems relaxed, switching between German and English – even mischievous. Rehearsing his objections to the "annexation" of East Germany in 1990, he scowls theatrically, "you're speaking with an angry old man", but laughs with good humour. He looked forward to marking his 83rd birthday this month with friends. As for fearing death: "No, I'm astonished with each new spring. At my age, every year is like a gift."