False Dmitry the First. False Dmitry I reigned as the Tsar of Russia from 10 June 1605 until his death on 17 May 1606. The first, and most successful, of three 'pretenders' who claimed during the Time of Troubles to be the youngest son of Ivan the Terrible, tsarevich Dmitry Ivanovich, who had supposedly escaped the 1591 assassination attempt when he was 8 years old.