A fortified town on the Seine between Rouen and Paris, burned by William the Conqueror in 1087 in the campaign that killed him, and the place where Philip II of France died in 1223.
Mantes, now Mantes-la-Jolie, sits on the left bank of the Seine some fifty kilometres downstream from Paris. Its position made it strategically awkward for everyone: it lay on the river road between the two centres of power in northern France, at the edge of the Vexin, the county that both the dukes of Normandy and the kings of France claimed.
A bridge, a castle and a walled town on that frontier meant that Mantes was garrisoned, raided and negotiated over for two centuries. The town's two famous days both involve a king who came to it from one side of that border or the other.
The Vexin was divided in the tenth century between a Norman half, west of the river Epte, and a French half toward Pontoise and Mantes. Neither half was securely held, and the frontier generated a long series of small wars quite out of proportion to the territory involved.
For the Norman dukes the French Vexin was the corridor down which a Capetian army would come; for the kings in Paris the Norman Vexin was the springboard from which a duke could threaten the royal domain. Mantes sat on that seam, which is why William the Conqueror attacked it in the last summer of his life.
In the summer of 1087 William, by then king of England as well as duke of Normandy, moved against the French Vexin, provoked according to Orderic Vitalis by a mocking remark of Philip I of France about the king's girth. He took Mantes and burned it, church and town together.
In the sack he suffered the injury that killed him — the usual account has him thrown hard against the pommel of his saddle, with a fatal internal rupture, though some sources describe illness rather than a wound. He was carried to the priory of Saint-Gervais outside Rouen and died there on 9 September 1087, leaving Normandy to Robert Curthose and England to William Rufus.
Philip II Augustus died at Mantes on 14 July 1223, on his way from Pacy toward Paris, in the forty-fourth year of a reign that had transformed the French monarchy. He was buried at Saint-Denis.
He left a kingdom roughly three times the size of the one he inherited. The conquest of Normandy from King John in 1204 had removed the Plantagenet duchy that made towns like Mantes frontier posts in the first place, and the victory at the Battle of Bouvines in 1214 had secured the result against a coalition of the Emperor Otto IV, the count of Flanders and the English king. By the time Philip died in the town, Mantes was no longer on a border at all.
The collegiate church of Notre-Dame, rebuilt from the later twelfth century on the ruins of the church William burned, is the principal survival: a large early Gothic building with a western rose, closely related in plan and elevation to the cathedral of Paris, and restored with royal money in Philip's reign.
Mantes kept a communal charter and a bridge toll, and its position on the Seine kept it prosperous through the later Middle Ages. It changed hands repeatedly in the Hundred Years War, and the bridge that made it valuable made it a target again in 1944.