The evidence implying surrender is contained in a letter written by Dzhugashvili's brigade commissar, Alexei Rumyanzev, to the Red Army's political director.
It insists that Stalin's son behaved "fearlessly and impeccably" as a battery commander.
But it goes on to explain how after his battery was bombed by the Nazis, Dzhugashvili and a Red Army soldier named Popuride escaped.
"They buried their papers and put on civilian clothing," the letter states.
But it adds: "When they reached the lakeside, Comrade Dzhugashvili told Popuride to keep going, but said that he wanted to stay and rest."
Der Spiegel said the admission that Stalin's son had wanted to "stay and rest" indicated that he had handed himself over. Independent