A spokesman for the public prosecutor’s office in Hanover, Germany, told German news sources that Mr. Groening’s lawyer confirmed the death. No other details were disclosed.
After training as a bank clerk, Mr. Groening joined the Waffen SS, an elite paramilitary branch of Germany’s Nazi regime in 1939 when he was 18. He spent more than two years at Auschwitz, a death camp in occupied Poland, where more than 1 million people were killed during the war.
One of his jobs was to retrieve the luggage of Holocaust victims and confiscate their money. He recorded the amounts for the camp’s “foreign currency department,” carefully noting whether the cash came from France, Great Britain, Greece, Italy, the United States or other countries. He sent the money to SS headquarters in Berlin.
“I do not feel myself guilty,” Mr. Groening told the German newspaper Hannoversche Allgemeine Zeitung in 2013, “because I didn’t give anyone so much as a slap in the face.”
Later, after encountering Holocaust deniers among his fellow Germans, Mr. Groening became one of the few death-camp guards to describe what he had witnessed.
“I see it as my task, now at my age, to face up to these things that I experienced and to oppose the Holocaust deniers who claim that Auschwitz never happened,” he told the BBC in 2004. “I want to tell those deniers I have seen the gas chambers, I have seen the crematoria, I have seen the burning pits — and I want you to believe me that these atrocities happened. I was there.”
As a self-described “small cog in the gears” who said he was not an active participant in killing, Mr. Groening believed he would not be prosecuted. “Where would you stop?” he said in 2013. “Wouldn’t you also have to charge the engineer who drove the trains to Auschwitz? And the men who ran the signal boxes?”
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He had been cleared of charges by a war-crimes tribunal in 1948, and German authorities investigated him again in the 1970s and 1980s before determining there was too little evidence to charge him.
His case was reopened after the 2011 conviction in Germany of John Demjanjuk, a onetime guard at the Sobibor camp in occupied Poland who later settled in the United States. (Demjanjuk died in 2012 while his case was being appealed.)
At Mr. Groening’s trial in 2015, he was charged with complicity in the murder of 300,000 Hungarian Jews between May and July of 1944.
“Because of my job in Auschwitz, I am without question morally complicit in the killing of millions of people, most of whom were Jews,” he said during his first day on the stand. “I ask them for forgiveness. Whether I am legally guilty is a matter this court must decide.”
He recalled scenes that remained shocking more than 70 years later. He watched as a fellow German soldier picked up a crying baby by its legs “and smashed it again and again against the iron side of a truck until it was silent.”
Mr. Groening said he told his superior officer about the incident the next day and requested a transfer, but was turned down.
Some observers found him sympathetic, and many Germans thought it unseemly to bring charges against a man in his 90s who struggled to reach the witness stand with his walker. But several survivors who lost family members at Auschwitz also provided compelling testimony at the trial and noted that Mr. Groening never made a formal apology in court.
“Any person who wore that uniform in that place,” said 84-year-old Irene Fogel Weiss, who lost 19 family members in Auschwitz, “represented terror and the depths to which humanity can sink, regardless of what function they performed.”
In July 2015, Mr. Groening was found guilty.
“You didn’t want to stand on the sidelines,” the judge, Franz Kompisch, told him. “What you, Mr. Groening, see as moral guilt is exactly what the law sees as accessory to murder.”
Mr. Groening’s appeals were rejected and, in November 2017, a German court determined that he was fit to begin serving his four-year sentence.
Oskar Groening was born June 10, 1921, in Nienburg, Germany. He was 4 when his mother died, and he was raised by his father, a stern factory worker and World War I veteran.
Mr. Groening joined the Hitler Youth group in his early teens. After Auschwitz, he was transferred to the front lines late in 1944 and was captured by British troops after being wounded.
He returned to Germany in 1948 and held administrative positions at a Lueneberg glass factory until his retirement in the 1980s. He was a widower and had two sons, but complete information about survivors was not immediately available.
Mr. Groening was one of about 6,500 SS guards at Auschwitz. He was the 50th to be convicted of war crimes. Another former guard, Reinhold Hanning, who was convicted in 2016 of being an accessory to the murder of more than 170,000 people, died last year without serving time in prison.
In a 2014 interview with the Daily Mail newspaper in Britain, Mr. Groening said he was forever haunted by what he saw at Auschwitz.
“Every night and every day I remember it for the nightmare it was,” he said. “Down the years I have heard the cries of the dead in my dreams and in every waking moment. I will never be free of them.”
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