The neighbouring Rech Pospolitaya State (the Polish-Lithuanian State) was impatiently waiting for any occasion to interfere in domestic affairs of weakened Russia. The Galich nobleman Yury (Grigory) Otrepyev, who had become a monk of the Chudov Monastery, ran in 1602 to Lithuania and there declared that he was Tsarevich Dmitry, the son of Ivan IV, saved by a miracle in Uglich on May 15, 1591.
Most probably he was a protege of disgraced boyards the Romanovs. In the beginning the Polish King Sigizmund III helped the impostor secretly. With assistance of governor of province Yury Mnishek (whose daughter Maria was to become the wife of Otrepyev) Lzhedmitry I gathered an army of mercenaries, 4 thousand strong.
In October, 1604 Lzhedmitry entered the southern areas of the country that were in revolt. A number of cities came over to the impostor's side. His army was also reinforced by the troops of the Don and Zaporozhye Cossacks. Local rebels joint the army as well. By the beginning of 1605 "Tsarevitch" had mustered more than 20 thousand people. The battle with the Tsar's Army commanded by Prince F.I. Mstislavsky took place on January 21, 1605 near Dobrynichi Village (Kamaritskaya Volost). Lzhedmitry I was totally defeated. Still, by miracle, he managed to flee to Putivil.
In this critical for the impostor period Tsar Boris Godunov suddenly died on April 13, 1605. His 16-years son Feodor came to the throne. The boyards refused to recognize the new Tsar. On May 7 the Tsar's Army headed by voevode Peotr Basmanov and Princes the Golitsinys came over to the side of Lzhedmitry I. The Boyards-conspirators organized coup d'etat on June 1, 1605. That provoked disorders in the capital. Tsar Feodor was dethroned and strangled together with his mother.
On June 1, 1605 Moscow swore allegiance to the impostor who settled in the Kremlin. However, hopes for a "kind and just" tsar were ruined before long. The Russian throne was now occupied by the Polish protege. Foreigners flooded the capital and behaved as if they were in a conquered city. Over the whole country people spoke openly that the Monomah's Crown was now possessed by a fugitive monk. The boyards did not need a tsar-adventurer any longer. A new plot was preceded by a wedding of Otrepyev and Marina Mnishek (a Catholic was crowned with a crown of the Orthodox state). Moscow was in a rage. On the night of May 17, 1606 a rebellion of the city population flared up. Conspirators rushed into the Kremlin and killed Lzhedmitry I.