Following the death of Henry I, medieval England was plunged into a civil war that reduced the country to a charred ruin. With the barons split between rival claimants, the people suffered. Stephen and Henry II, from Les Roys de Engeltere, Anglo-Norman manuscript, late 13th century. © British Library Board.

All Rights Reserved / Bridgeman Images. In the summer of 1153, a broken man agreed to disinherit his son to end a war that had splintered England for 19 years. The reign of King Stephen (1135-54) was a disaster, later dubbed 'the Anarchy'.

Henry I, having lost his only legitimate son in the wreck of the White Ship in 1120, named his daughter Matilda as his heir. She was residing in Germany as the wife of Emperor Henry V. His early death in 1125 allowed Matilda to return to Normandy and position herself as heir.

Designating a woman as successor was unprecedented; Henry compelled nobles to swear an oath of allegiance to Matilda. All did so, though some complied with reluctance. Henry's death in December 1135 caught Matilda off guard; her cousin Stephen, a younger son of Henry's sister Adela, rushed to England, seized the treasury, and had himself crowned.

Though many had sworn to uphold Matilda's rights, there was barely a murmur due to her being female. Had Henry left the crown to a son, such a situation would not have arisen. Hampered by pregnancy and lack of means, Matilda could do nothing as Stephen usurped the throne.

After a couple of years, she marshaled resources, aided by the defection of her illegitimate but rich and powerful half-brother Robert, the earl of Gloucester. She sailed for England in September 1139, beginning the first active phase of the war. No king or queen could rule without noble support.

Initially, there was a stark divide. On Matilda's side were those loyal to Henry I who wished to install his only surviving legitimate child. Against them were those who preferred Stephen as a known, male quantity.

Nobles on both sides were motivated by personal gain. Stuck in the middle was the population of England, who tilled the land, manufactured, traded, paid taxes, and were liable to fight for their local lords. The sinking of the White Ship from Peter Langtoft's Chronicle of England, early 14th century.

Pictorial Press Ltd / Alamy Stock Photo. King or queen? The first hint of a swing away from Stephen was caused by the king himself. In four years, Stephen had proven ineffective, rushing up and down the kingdom quelling small-scale revolts and showing undue leniency that encouraged further dissent.

Contemporary chroniclers noted the king's desire to settle all things...