The Anarchy was a civil war in England and Normandy between 1138 and 1153 which resulted in a widespread breakdown in law and order. The conflict was a war of succession precipitated by the accidental death of William Adelin—the only legitimate son of King Henry I—who drowned in the White Ship disaster of 1120. Henry then sought to leave the English throne to his daughter, Empress Matilda, but was only partially successful in convincing the nobility to support her. On Henry's death in 1135, his nephew Stephen of Blois seized the throne with the help of his brother Henry of Blois, bishop of Winchester. King Stephen's early reign saw fierce fighting with disloyal English barons, rebellious Welsh leaders, and Scottish invaders. Following a major rebellion in the southwest of England, Matilda invaded in 1139 with the help of her half-brother Robert of Gloucester.