Stephen ascended to the throne in 1135 following the death of his uncle, Henry I. Although he was the grandson of William the Conqueror, his claim to the crown was immediately contested by his cousin, Empress Matilda, who was the daughter of the late king. This dispute triggered a protracted and devastating period of civil war that became widely known as the Anarchy, a time characterised by widespread lawlessness and the collapse of centralised governance across England.

Throughout his nineteen-year reign, Stephen struggled to maintain control as the country descended into chaos. The conflict saw shifting loyalties among the nobility and frequent military engagements, which significantly eroded the power and prestige of the monarchy. The instability was so profound that it became difficult for the king to enforce royal authority, leading to a breakdown in the administration of justice and the fortification of unauthorised castles by local barons.

The struggle for the throne eventually reached a stalemate, as neither side could secure a decisive victory over the other. Recognising the exhaustion of the realm and the need for a peaceful resolution, a formal settlement was eventually negotiated. This agreement, known as the Treaty of Wallingford, secured the succession for Henry Plantagenet, the son of Empress Matilda, who would later be crowned as Henry II.

Key aspects of this period include:

• The contested succession following the death of Henry I.
• The prolonged civil war between Stephen and Empress Matilda.
• The significant weakening of royal authority and central government.
• The eventual compromise that established the Plantagenet dynasty.

Stephen remained on the throne until his death in 1154, at which point the crown passed to Henry II. This transition marked the end of the Norman line of kings and the beginning of the Angevin era. The legacy of Stephen's reign is largely defined by the turbulent nature of the Anarchy and the subsequent reforms initiated by his successor to restore order and royal influence throughout the kingdom.