The Time of Troubles or Smuta , was a period of political crisis during the Tsardom of Russia which began in 1598 with the death of Fyodor I (Fyodor Ivanovich, the last of the Rurik dynasty) and ended in 1613 with the accession of Michael I of the House of Romanov.
It was a time of lawlessness and anarchy following the death of Fyodor I, a weak and possibly intellectually disabled ruler who died without an heir. His death ended the Rurik dynasty, leading to a violent succession crisis with numerous usurpers and false Dmitrys (imposters) claiming the title of tsar.
Russia experienced the famine of 1601–03, which killed almost a third of the population, within three years of Fyodor's death. Russia was occupied by the Polish–Lithuanian Commonwealth during the Polish–Russian War (also known as the Dimitriads) until it was expelled in 1612. It was one of the most turbulent and violent periods in Russian history. In just 15 years, the crown changed hands six times. Estimates of total deaths caused by the conflict range from 1 to 1.2 million, while some areas of Russia experienced population declines of over 50 percent.
The Time of Troubles ended with the election of Michael Romanov as tsar by the Zemsky Sobor in 1613, establishing the Romanov dynasty, which ruled Russia until the February Revolution in 1917.
Reference
https://en.m.wikipedia.org/wiki/Time_of_Troubles