The Anarchy was a civil war in England and Normandy between 1135 and 1154, which resulted in a widespread breakdown in law and order. The conflict began with a succession crisis towards the end of the reign of Henry I, when the king's only legitimate son, William Adelin, died aboard the White Ship in 1120. Henry's attempts to install his daughter, the Empress Matilda, as his successor were unsuccessful and on Henry's death in 1135, his nephew Stephen of Blois seized the throne with the help of his brother, Henry, bishop of Winchester. Stephen's early reign was marked by fierce fighting with English barons, rebellious Welsh leaders and Scottish invaders. Following a major rebellion in the south-west of England, Matilda invaded in 1139 with the help of her half-brother, Robert of Gloucester.