Ironclad

In the prologue, the barons of England, aided by the Knights Templar, wage a war against King John that lasts more than three years. Magna Carta is forced upon the King, granting rights to freemen and limiting royal power. In a later twist, John regrets signing Magna Carta and hires an army of pagan Danish mercenaries led by the warlord Tiberius to restore his absolute authority.

Abbot Marcus guides three Templar knights on a pilgrimage toward Canterbury. They seek shelter from the rain at Darnay Castle, where they pause to rest and plan their route. Marshall is assured that his release from the Templar Order will be sought at Canterbury.

By morning, King John arrives with his army and Danish mercenaries. Baron Darnay signs Magna Carta and is executed in retaliation for his act, while the Abbot is ordered to have his tongue cut out. The castle's defenders are left reeling as the King's power asserts itself.

Marshall and his two fellow knights fight the Danes to cover a retreat. Marshall escapes on horseback, carrying the wounded Abbot, while the other two knights are slain. The Abbot dies of his wounds, and Marshall breaks his vow of silence to declare that his sacrifice will not be in vain.

Marshall reaches Canterbury and meets Archbishop Langton and Baron William d'Aubigny. Langton reveals that the Pope has sided with King John and that he himself faces excommunication for Magna Carta. The trio resolves to stop John at Rochester Castle, a strategic stronghold in the rebellion.

Aubigny gathers support, recruiting three men along with his squire Guy and the petty criminal Jedediah. A fourth man declines, leaving seven fighters ready to march on Rochester. They depart Canterbury to strike at the stronghold and challenge John's control.

Arriving at Rochester, Aubigny's party finds Danish mercenaries already inside. They fight and kill the Danes, claiming Rochester Castle for the rebellion, much to Cornhill's displeasure. The castle becomes a new focal point in the struggle against John.

John's army arrives and lays siege to Rochester Castle. The garrison repels the initial Danish assault, and the siege settles into a grinding contest as resources dwindle. The Archbishop learns that Prince Louis is waiting in France and negotiates with John to hasten an end to the conflict.

As winter approaches, hunger gnaws at the defenders. Marshall slips out at night to raid the Danish camp and returns with food to bolster morale. His actions coincide with a forbidden entanglement with Isabel, Cornhill's wife, breaking his Templar vows.

Tiberius orders a new tactic, slipping a small force over the walls to open gates from within. Guy discovers the breach and raises the alarm, but Tiberius leads the assault into the castle grounds, slaughtering the garrison.

During the second assault, Aubigny is dragged before King John and forced to watch as the hands of two prisoners are chopped off; after a defiant exchange, he meets the same fate and is hurled by the castle trebuchet into a keep wall. Cornhill attempts to surrender but ends his life by hanging. John's engineers have prepared a mine beneath the keep's foundation, using pigs and fat to fuel its destruction.

With the keep crumbling, the last defenders fall; Guy, Isabel, and Marshall remain. Marshall recovers and engages in a savage duel with Tiberius, emerging victorious. The distant horns announce the arrival of the combined English rebel and French army, forcing John and the Danes to retreat in panic.

At the gates, Marshall meets Prince Louis and Archbishop Langton; Langton proclaims that Marshall is free of the Templar Order. He and Isabel ride away together as Guy salutes the fallen baron and says, 'We held.'

King John's death occurs during his retreat, and Rochester Castle is rebuilt to stand as a lasting symbol of Magna Carta. The stronghold endures as a testament to the rebellion and the enduring rights won for English freemen.