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Ivan the Terrible, the notorious Soviet war criminal, was the mistaken identity given to John Demjanjuk during his trial in Israel. Demjanjuk, a Ukrainian-born former autoworker, was initially believed to be Ivan the Terrible, a brutal concentration camp guard known for his cruelty. However, extensive investigations and historical evidence later revealed that Demjanjuk was not, in fact, Ivan the Terrible, leading to a reassessment of his case and eventual exoneration.