Complex sentence: As they advanced, as-Salih Ayyub died and was succeeded by his son al-Muazzam Turanshah, but before Turanshah could arrive at the front, the Bahri mamluks defeated the crusaders at the Battle of Al Mansurah and captured Louis, effectively ending the crusade.
Split into simpler sentences: As they advanced, as-Salih Ayyub died and was succeeded by his son al-Muazzam Turanshah. Before Turanshah could arrive at the front, the Bahri mamluks defeated the Crusaders at the Battle of Al Mansurah and captured Louis, effectively ending the crusade.