Siege of Mountsorrel Castle (1217)
Who Fought
History & Significance
During the First Barons' War in 1215–17, Dover Castle was twice besieged by Anglo-French forces under Prince Louis of France. It has also been described as a single siege, with a truce separating it into two distinct phases.
In the first phase in 1216, Louis' forces breached the walls, but were repulsed by the defenders. A truce was struck, and Louis withdrew to London. The second phase in 1217 proved brief; news of the Capetian defeat at the Battle of Lincoln prompted Louis to withdraw and begin peace negotiations.
The Angevin and Capetian dynasties had, for decades, been embroiled in a bitter rivalry. The Angevins were French dukes, nominally subjects of the Capetian kings of France, but their control of the kingdom of England had elevated them to peers of the Capetians.
In 1204 the Capetians had firmly claimed the upper hand in their ongoing contest, conquering Normandy and crippling the Angevin presence in France. King John of England had attempted to reconquer his French possessions in 1214, but his allies had suffered a devastating defeat at the Battle of Bouvines, and he had been forced to withdraw.
Noble discontent towards John reached a fever pitch, and in 1215 he had been forced to sign Magna Carta, a document severely curtailing the crown's powers. His subsequent refusal to abide by Magna Carta had resulted in the outbreak of the First Barons' War, a large-scale rebellion against the king. The rebellious barons invited Prince Louis of France to take the throne, and he arrived in England on 21 May 1216; an Angevin force had gathered to oppose him, but withdrew without giving battle.
Dover Castle occupied a key strategic position on the south coast of England, overlooking the English Channel; as such, it was regarded as the 'Key to England' and a "lynchpin" in the Angevin Empire. As such, it was one of Louis' most important targets. He began the siege in May 1216, first moving to encircle the castle, while his naval forces cut off the defenders' access to the sea. He then began construction of a siege tower, and started undermining the walls. He also deployed artillery including perriers and mangonels. During this initial phase, the defending forces under Hubert de Burgh made several sorties from the castle, disrupting the besiegers.
In August, Louis' knights stormed and captured the timer palissade of the outer barbican, following successful undermining. The besiegers were bolstered by good news, as the Capetians' new ally Alexander II of Scotland arrived to do homage to Louis, and a number of reinforcements arrived from France. In September, the besiegers' undermining created a breach in the walls, which they promptly stormed; however, they were repulsed by the defenders, who then barricaded the breach.
The ground they fought on
The site of Siege of Mountsorrel Castle (1217) lies on Triassic Rocks (Undifferentiated), bedrock that formed in the Triassic. The rock here is mudstone, siltstone and sandstone.
The most striking detail of the Mountsorrel episode is the sheer scale of the relief force Louis dispatched: some 20,000 men sent northward specifically to break the English siege. Far from being a footnote, this was one of the largest Capetian field armies committed anywhere in England during the entire war. Yet despite this enormous numerical superiority, the relief effort ultimately achieved nothing lasting, because Louis's commanders squandered the advantage by redirecting those very troops to Lincoln, leaving Mountsorrel unprotected and allowing the English to return and level the castle without resistance.
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- Sieges of Dover Castle (1216–17) · Wikipedia
- 1217 · Wikipedia