The judge's acquittal of Demjanjuk for being Ivan the Terrible was based on the written statements of 37 former guards at Treblinka that identified Ivan the Terrible as "Ivan Marchenko". The former guards' statements were obtained after World War II by the Soviets, who prosecuted USSR citizens who had assisted the Nazis as auxiliary forces during the war. Most of the guards were executed after the war by the Soviets, and their written statements were not obtained by Israeli authorities until 1991, when the Soviet Union collapsed. Central to the new evidence was a photograph of Ivan the Terrible and a description that did not match the 1942 appearance of Demjanjuk. The accounts of 21 guards who were tried in the Soviet Union on war crimes gave details that differentiate Demjanjuk from Ivan the Terrible – in particular that 'Ivan the Terrible's surname was Marchenko, not Demjanjuk. One described Ivan the Terrible as having brown hair, hazel eyes and a large scar down to his neck; Demjanjuk was blond with grayish-blue eyes and no such scar. US officials had originally been aware, without informing Demjanjuk's attorneys, of the testimony of two of these German guards. However the Israeli justices noted that Demjanjuk had incorrectly listed his mother's maiden name as "Marchenko" in his 1951 application for US visa. Demjanjuk said he just wrote a common Ukrainian surname after he forgot his mother's real name (Tabachyk).