Complex sentence: During his second crusade, Louis died at Tunis, 25 August 1270, and was succeeded by his son, Philip III. Louis was traditionally believed to have died from the bubonic plague but the cause is thought by modern scholars to have been dysentery.
Split into simpler sentences: During his second crusade, Louis died at Tunis, 25 August 1270. He was succeeded by his son, Philip III. Louis was traditionally believed to have died from the bubonic plague but the cause is thought by modern scholars to have been dysentery.