PARIS, Aug. 16 — In novels, plays, essays and newspaper interviews, Günter Grass has often told Germans what they did not want to hear: about their history, about their politics, even about themselves. For many on the left, since the 1960’s he has come to represent the conscience of a country with much to lament.

After winning the Nobel Prize in Literature in 1999, he explained his obsession with Germany’s past. “There were extenuating circumstances,” he told the Swedish Academy, “mountains of rubble and cadavers, fruit of the womb of German history. The more I shoveled, the more it grew. It simply could not be ignored.”

But now, at 78, Mr. Grass has stunned Germany by confessing that he too has a buried past. In an interview with a leading German newspaper, he revealed that in the final months of World War II, when he was 17, he was drafted by the Waffen SS, the military branch of the notorious Nazi corps that played an important role in the Holocaust and other atrocities.

The reaction in Germany to this admission has been one of disbelief and indignation: not that a teenager should have been recruited into the Waffen SS as Hitler struggled to avoid defeat, but that the country’s most prominent writer should have hidden this while hectoring others for their political and social sins from the comfort of the moral high ground. “I do not understand how someone can elevate himself constantly for 60 years as the nation’s bad conscience, precisely in Nazi questions, and only then admit that he himself was deeply involved,” Joachim Fest, a prominent historian and biographer of Hitler, told the newspaper Bild. “I don’t know how he could play this double role for so long.”