In June 861, Charles the Bald (823, † 877) summons the annual general plea in the royal villa of Pîtres, asking the adults to come accompanied by workers and tanks. He then gives the order to start the construction of a fortified bridge spanning the courses of the Seine and the Eure in order to block the road to the Viking fleets which infest the valley. Then began one of the largest projects of the time which lasted nearly ten years and mobilized an enormous workforce.
Viking raids in the lower Seine valley
The first appearance of a Viking fleet in Neustria dates from the year 820. Entering the Seine estuary, it meets the guards of the coastal defense set up by Charlemagne in the ports and at the mouths of rivers. The fight begins; the Vikings lose men and turn back. This coastal defense protects the lands of Francia until the death of Louis le Pieux (778, † 849).
In 841, the Vikings, led by a chief named Oscherus after the Chronicle of Fontenelle - Ásgeirr in Norse -, again invest the lower valley of the Seine, without encountering resistance. They sack Rouen, plunder the abbey of Saint-Ouen, devastate the abbey of Jumièges and spare St Wandrille de Fontenelle against the payment of six thousand gold pounds.
Four years later, in 845, a second incursion took place. One hundred and twenty ships led by Ragnarr aux Braies Velues - Ragnar Lodbrok - dock in Rouen. They burn the Celle monastery, then they reach the suburbs of Paris where they devastate the monasteries of Sainte-Geneviève and Saint-Germain, while King Charles the Bald, powerless, has taken refuge in Saint-Denis. The latter ends up buying the departure of the Vikings against the sum of seven thousand pounds of silver.
In 851 and 852, new fleets entered the Seine, plundered the abbey of Saint Wandrille de Fontenelle and, for the first time, wintered there, probably on the island of Jeufosse - Fossa Givaldi. In 855, Sydroc went up the Seine to Pîtres. He is joined by another fleet, commanded by the Viking leader Björn Côtes de Fer - Björn Járnsíða -, one of the four sons of Ragnarr of the Hairy Breeches. Rouen is sacked again. The two armies established themselves on the island of Oscellus - Oissel upstream of Rouen, present-day Île Sainte-Catherine, which the Vikings renamed Þorhólmr, the islet of Þórr - and, from this base, they ravaged the two shores of the Seine, pushing up to Perche and Chartres. December 856, they are under the walls of Paris.
In 858, Hásteinn presented himself at the mouth of the Dives, entered the city of Chartres on June 12 and looted the cathedral. The bishop dies while fleeing, carried away by the course of the Eure which he tries to cross. In the same year, Bayeux is also devastated, its bishop slaughtered. In the midst of Easter, Louis, Abbot of Saint-Denis, archichapelin of King Charles the Bald, is captured with his half-brother Gauzlin, future bishop of Paris. Both are only released for a heavy ransom.
July 858, Charles the Bald, assisted by his nephew Lothaire II, lays siege in front of the island of Oissel, in order to dislodge the Vikings who infest his kingdom. But, he must give up after three months, because his brother Louis the German took the opportunity to enter his kingdom, with the intention of dethroning him. In 860, when the Vikings of Hásteinn attacked Paris for the third time, Charles the Bald promises the Viking mercenary Völundr the sum of three thousand pounds if he manages to drive Hásteinn and his allies from the island of Oissel. Völundr accepts the contract. In 861, he stationed at the villa of Pîtres when he received the money from Charles. To establish the blockade of the island, some of these boats go up the Andelle, then they are sunk over a few kilometers of dry land before being put back afloat, thus taking the besieged from the rear. Soon, these, starving, negotiate with their attackers. They in turn pay Völundr six thousand pounds of gold and silver to let them go.
The fortified bridge of Pont de l'Arche
The following year, Charles le Chauve decides to build the fortified bridge over the Seine. Others were also built, one on the Marne at Trilbardou, a second on the Seine near Paris, which moreover remained unfinished during the siege of 885. The works lasted ten years. Each major is assigned a section of the bridge to build, for which he must provide the necessary workers and materials. Chariots with oxen as well as young "esteaudeaux" - young serf or unmarried vassal - must also be brought, the esteauudeaux having to keep garrison to defend the bridge.
The bridge is built of stone and wood. At each of its ends rises a fortified work - a castellum - whose role is to protect the entrances to the bridge and also to shelter the garrisons responsible for its defense. These works are made of stone while the bridge itself, its pillars, its deck and the crenellations of the fortifications are made of wood. The bridge rises across the courses of the Seine and the Eure, at the meeting point of the two rivers. On the left bank, the châtelet stands at the level of the current town of Pont-de-l'Arche, where there was a priori a port, Portus Devenna, with its houses, its smugglers conveying ferries from one bank to the other, its fishermen and its inns. On the right bank, the other tower stands around the town of Igoville, at a place called Limaie. This is where the ancient road leading to Vieil-Evreux ends and, moreover, the road leading to the royal domain of Pîtres.
In his article , by observing the topography of the town of Pont-de-l'Arche, Jacques le Maho suggests that the Carolingian village took place at the level of the current parish church, Saint-Pierre. The circular street surrounding the church recalls the walls of the old town and the chatelet, with two gates, respectively located to the east and to the west. The châtelet undoubtedly rose, in the center of this enclosure, at the level of the current church, which then was only a simple oratory for the travelers. On the other bank, Philippe Auguste undoubtedly had Fort Limaie built on the site of the Carolingian chatelet. The Saint-Etienne chapel of this fort would also originate from a Carolingian oratory attached to the entrance to the fortified bridge, exactly in the same arrangement as on the other bank.
The future of the Pont de l'Arche fortified bridge
In 865, a Viking fleet ran aground in front of the bridge under construction. The king, not daring to force the attackers into their entrenchments, had the rivers upstream, the Oise at Auvers, the Seine and the Marne at Charenton, fortified. The Vikings however attacked Chartres, Paris, then they plundered the abbey of Saint-Denis. They set sail again in July 866, against the payment of a tribute of four thousand pounds. In 876, a new fleet entered the valley of the Seine and collided with the bridge which it tried in vain to take. The Vikings ravaged the region, forcing the Archbishop of Rouen to flee. Once again, Charles the Bald buys their departure for the sum of five thousand pounds.
There are no other threats before the year 885, which tends to show the effectiveness of the bridge. That year, a Viking army stationed in Louvain moved on foot to Rouen, chased by the troops of King Charles the Fat (839, † 888). She entered the city on July 25 and, using the boats moored there, she crossed the Seine and took refuge on the right bank, awaiting reinforcements from the river, from the Scheldt and England. The junction made, this army came to settle about a kilometer from the fortified bridge, in the locality known as Les Damps. The Vikings fortified their position, surrounding their camp with a high circular mound of earth. The soldiers of Charles the Fat also receive reinforcements, Frankish and Burgundian troops led by Duke Ragenold. The latter decides to attack the encampment of the Vikings at dawn, while it seems that they are sleeping. The Franks ride, rush into the camp; the Vikings who, lying on the ground, pretend to be asleep, get up and massacre all those who are within their reach. Ragenold is killed; the rest of the army flees. The Vikings leave their camp, take the bridge and deliver it to the flames. Then, they embark for Paris, to lay siege in front of the city until the fall of 886, after having taken Pontoise.
The bridge will not be raised. It will have allowed a lull of ten years in the long series of Viking incursions via the course of the Seine.
• Jean Renaud, the Vikings in France, Editions Ouest France.
• Jean Renaud, Normandy of the Vikings, Orep Editions
• Laurent Mazet-Harhoff, “In the footsteps of the Vikings in Upper Normandy: problematic”, p119-151, in “the progression of the Vikings, from raids to colonization, Les cahiers du GRHIS, n ° 14, 2003.
•  Jacques Le Maho, “A great royal work of the 9th century: the fortified bridge known as“ de Pîtres ”in Pont-de-l'Arche (Eure), Castles and sources: archeology and history in medieval Normandy : mixtures in honor of Anne-Marie Flambard Héricher, Bruno Lepeuple, Jean-Louis Roch, January 1, 2008, Publication Rouen Havre University
• Edouard Favre, Eudes, count of Paris and king of France (882 - 898), Honoré Champion, Paris