Some historians call Mustafa I as Mustafa the Mad (Deli Mustafa in Turkish), believing that he was mentally imbalanced when he came to the throne. He ruled the Empire twice, between 1617-1618 and 1622-1623.
When Sultan Ahmed I, Mustafa's older half-brother, died in 1617, his son Osman was too young to be enthroned without causing problems in the State. Therefore Mustafa I became the next sultan and this was the first time an Ottoman Sultan was succeeded by his brother instead of his son. Due to Mustafa's mental conditions, his mother Halime Sultan (the Queen Mother or Valide Sultan) acted as regent during her son's rule. After a short rule of one year, the court faction deposed him in favor of his young nephew Osman II. But when Osman II was out-throned and assassinated during a Janissary rebellion in 1622, Mustafa was restored to the throne and ruled for another year. During his second rule, the conflicts between various corps of the army, political instability, and Mustafa's mental condition brought his rule to an end and to his deposition for the second time. Murad IV, son of Ahmed I and Kosem, was enthroned in 1623.