False Dmitry I  Dmitry I () (historically known as Pseudo-Demetrius I and False Dmitry I, ) reigned as the Tsar of Russia from 10 June 1605 until his death on 17 May 1606 under the name of Dmitry Ivanovich (). According to historian Chester S.L. Dunning, Dmitry was "the only Tsar ever raised to the throne by means of a military campaign and popular uprisings". He was 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 a 1591 assassination attempt. It is generally believed that the real Dmitry died in Uglich in 1591. Dmitry I entered history circa 1600, after making a positive impression on Patriarch Job of Moscow with his learning and assurance. Upon hearing of this, Tsar Boris Godunov ordered the young man to be seized and examined, whereupon Dmitry fled to Prince Constantine Ostrogski at Ostroh, of the Polish–Lithuanian Commonwealth, and subsequently entered the service of the Wiśniowieckis, a polonized Ruthenian family. Two family members in particular, the princes Adam and Michał Wiśniowiecki, were intrigued by the stories Dmitry told of whom he purported to be, as it gave the Poles real opportunity to capitalize on the political rancor rising in Moscow. There were rumors that Dmitry was an illegitimate son of the Polish king, Stefan Batory, who had reigned from 1575 to 1586; according to a later tale, Dmitry blurted out that identity when once slapped by a violent master. Dmitry's own story was that his mother (Tsar Ivan's widow), anticipating Boris Godunov's assassination attempt, had given the young tsarevich into the care of a doctor, who placed him in various Russian monasteries through the years. After the doctor's death, Dmitry had then fled to Poland, working there as a teacher for a brief time, before being accepted into the service of the Wiśniowieckis. Several of those who had known Ivan IV claimed later that Dmitry did indeed resemble the young tsarevich; further, the young man also displayed aristocratic tendencies, such as horsemanship and literacy, and was fluent in Russian, Polish, and French. However, regardless of whether or not Dmitry's tale was authentic, the Wiśniowiecki brothers, along with Samuel Tyszkiewicz, Jan Sapieha, Roman Różyński, and several other Polish noblemen soon agreed to fully back the man, and his claim, against Tsar Boris Godunov.