Stephen of England was the grandson of William the Conqueror through his daughter Adela. William's son William II had died childless; his other son Henry I had only one legitimate child alive, Matilda. Henry had designated Matilda heir to the throne and made many of his nobles, including Stephen, swear to support her. On Henry's death in 1135, though, Stephen went to London and induced the Archbishop of Canterbury to crown him king, claiming Henry had changed his mind on his deathbed. So many people were opposed to the idea of a woman on the throne that Stephen's claim was pretty popular. Matilda protested, but Pope Innocent II supported Stephen (and also Stephen bribed a lot of his former opponents), so for a while, the only problem in the country was warring with the Scots. Stephen won a great battle in August 1139 against them, and a peace was made on that front.

However, Matilda and her illegitimate half-brother Robert had been gathering armies in Europe, and invaded England in the fall of 1139. Fighting continued for several years, with both claimants to the throne getting captured or just barely escaping capture; no outcome was in sight. In 1153 Matilda's son Henry rallied her supporters, and with the objection of Matilda's gender removed, the Treaty of Westminster was concluded with Stephen keeping the crown for life, after which it would pass to Henry. (Stephen's children held their mother's lands in France.) Stephen died, probably of appendicitis, in 1154.