Complex sentence: Henry III died in 1272 and was succeded by his son, Edward I. Whereas Henry's ineffectiveness had led to the collapse of royal authority in England during his reign, Edward was a vigorous and forceful ruler and an able military leader.
Split into simpler sentences: Henry III died in 1272 and was succeeded by his son, Edward I. Henry's ineffectiveness had led to the collapse of royal authority in England during his reign. However, Edward proved to be a vigorous and forceful ruler and an able military leader.