sentences:  Regardless of the reason, Ivan's domestic and foreign policies had a devastating effect on Russia and led to a period of social struggle and civil war, the Time of Troubles ("Smutnoye vremya", 1598-1613).Ivan IV was succeeded by his son Feodor, who was mentally deficient.Actual power went to Feodor's brother-in-law, the boyar Boris Godunov (who is credited with abolishing Yuri's Day, the only time of the year when serfs were free to move from one landowner to another).