The Anarchy was a war in England and Normandy between 1135 and 1153, characterised by a breakdown in law and order. The conflict originated 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 took power with the help of his brother, Henry 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.