Complex sentence: According to the Shia, Husayn was the third Imam for a period of ten years after the death of his brother Hasan in 669, all of this time but the last six months coinciding with the caliphate of Muawiyah.
Split into simpler sentences: According to the Shia, Husayn was the third Imam for a period of ten years after the death of his brother Hasan in 669. All of this time but the last six months coinciding with the caliphate of Muawiyah.