Ernst Nolte, a German revisionist historian who broke academic taboos by equating Nazism with Bolshevism and who was denounced as an apologist for Hitler and even the Holocaust, died on Thursday in Berlin. He was 93.

His family told the daily newspaper Der Tagesspiegel that he had died in a hospital.

Professor Nolte, a respected scholar of fascism, provoked an ideological uproar in 1986 by suggesting in an essay that Nazisim had been a logical response in Germany to an “existential threat” posed by the Russian Revolution and its aftermath. He also argued that Hitler’s extermination of Jews and other minorities was comparable to the mass murders engineered by Stalin in the Soviet Union, where victims were singled out by economic and social class as enemies of the Communist state.

“Did the ‘Gulag Archipelago’ not exist before Auschwitz?” Professor Nolte wrote in the newspaper Frankfurter Allgemeine Zeitung. “Was Bolshevik ‘class murder’ not the logical and factual predecessor to the Nazi ‘racial murder’?” he continued. “Did Auschwitz not, perhaps, originate in a past that would not pass away?”

An intellectual firestorm ensued — his car, parked at the Free University in Berlin, where he taught, was set ablaze — but Professor Nolte was nevertheless awarded the Konrad Adenauer Prize for literature in 2000 by the Munich-based Deutschland Foundation, a conservative organization close to the Christian Democratic Party’s right wing.