The treaty of Saint-Clair-sur-Epte (911) is the foundational document of the Duchy of Normandy, establishing Rollo, a Norse warlord and Viking leader, as the first Duke of Normandy in exchange for his loyalty to the king of West Francia. The territory of Normandy centered on Rouen, a city in the Marches of Neustria which had been repeatedly raided by Vikings since the 840s, and which had finally been taken by Rollo in 876.
The talks, led by Hervé, the Archbishop of Reims, resulted in the Treaty of Saint-Clair-sur-Epte in 911. The treaty granted Rollo and his soldiers all the land between the river Epte and the sea "in freehold and good money". In addition, it granted him Brittany "for his livelihood." At the time, Brittany was an independent country which present day France had unsuccessfully tried to conquer. In exchange, Rollo guaranteed the king his loyalty, which involved military assistance for the protection of the kingdom against other Vikings. One of the conditions for the Vikings after their loss was to convert. As a token of his goodwill, Rollo also agreed to be baptized and to marry Gisela, a presumed legitimate daughter of Charles. The traité en forme at Saint Clair-Sur-Epte marked the beginning of Normandy as a state.
With Norse bands of settlers, composed of non-aristocratic lineages, there came multiple communities formed and a new political ethos that was not Frankish. The Norsemen ("Northmen") came to be known as Normans in French. This identity formation was partly possible because the Norse were adapting indigenous culture, speaking French, renouncing paganism and converting to Christianity, and intermarrying with the local population.
The territory covered by the treaty corresponds to the northern part of today's Upper Normandy down to the Seine, but the territory of the Vikings would eventually extend west beyond the Seine to form the Duchy of Normandy, so named because of the Norsemen who ruled it. The treaty allowed these new settlements. But not all Vikings were welcome. And with the death of Alan I, King of Brittany, another group of Vikings occupied Brittany faced their own dispute. Around 937, Alan I's son Alan II returned from England to expel those Vikings from Brittany in a war that was concluded in 939. During this period the Cotentin Peninsula was lost by Brittany and gained by Normandy.
There would be a convergence between Franks and Normans with a few generations. But for now, the treaty involved a marriage between Gisla and Hrólfr (also known Rollo to the Franks). Marriages such as this played an important role in cultivating alliances and cohesion; wives were often called "peace weavers." And later, Charles the Simple created an alliance and a grant of rights to those Vikings seeking to settle in 918.
While the Normans did adapt, adopt, and assimilate to Christianity, they did not necessarily adopt indigenous administration: "The creation of Norman power between first settlement and the mid-eleventh century is not primarily of assimilation to Carolingian forms, as those appear in the capitualaries. Rather, the Normans "adhered longer than the Franks around them--to older forms of social organization," that the Franks were abandoning.
The Normans came close to being absorbed into a lower social strata in Frankish society had not renewed wave of Viking raids occurred in the 960s. Over time, the frontiers of the duchy, based in kinship, expanded to the west. "By the mid-eleventh century the descendants of the settlers formed the most disciplined, cooperative warrior society in Europe, capable of a communal effort--the conquest and subjugation of England--that was not, and could not have been, mounted by any other European political entity."
There was not a successful duchy until around the time of Richard I control of Normandy. During his reign, he bore daughters who would become peace weavers to forge valuable marriage alliances with powerful neighboring counts and the king of England. His daughter, Emma, underwent two marriages. In 1002, King Æthelred II married Emma, the sister of Richard II, Duke of Normandy. After Æthelred the Unready's death in 1016, Emma married her second husband who was an invader, Cnut the Great. Emma and Æthelred the Unready's children included Alfred Aetheling and Edward the Confessor. Emma also bore children with Cnut: Haracnut and a daughter, Gunnhild. That is not to mention Cnut's previous child in his previous marriage: Harold Harafoot. While the complicated woven connections that marriage brought could bring peace, after the alliance of Cnut and Emma had ended was a battle over the throne. Emma's children with Æthelred the Unready give a major connection between Normandy and England that would later add validity to William the Conqueror's claim to the throne of England.
On 12 November 1035, King Cnut died at Shaftsbury in Dorset. He was around 40 years old and was buried at the Winchester Abbey. With his death, a succession crisis was created, and his huge Northern European empire, which contained England, Denmark and Norway fell apart because of strife over which heir would control certain regions. For instance, Harold Harefoot tried to seize the throne of England and was able to rule the "North of the river of Thames" until 1035 when he "failed to prevail over the archbishop." Meanwhile, south of the River Thames, Haracnut reigned "but w deserted by his supporters in 1037." In 1037, Harold Harefoot ascended the throne "as king everywhere," but with his death came the accession of Haracnut. Essentially, all of Cnut's children, whether illegitimate or not, had an interest in the throne of England, the male heirs.
Edward the Confessor was an illegitimate child of Cnut because he came from Emma's first marriage. Not being a direct son of Cnut meant that Edward and his brother spent most of their lives in Normandy as an exile to England. That dynamic led to the establishment of a powerful Norman interest in English politics. Edward drew heavily on his former hosts for support, bringing in Norman courtiers, soldiers and clerics and appointing them to positions of power, particularly in the Church. Edward was childless and embroiled in conflict with the formidable Godwin, Earl of Wessex, and his sons, and he may also have encouraged Duke William of Normandy's ambitions for the English throne." Therefore, he laid claim to the English throne while Haracnut was ling. Eventually, William would not only stake a claim to the English crown but also take advantage of the fragmented state of England because of the Great Succession Crisis and its aftermath.
Before William left for England, he had to gain support and unify Normandy as a consolidated state. However, to maintain that unity in Normandy meant William needed to make sure that his neighbors, such as France, were not a threat. William was able to leave for his invasion with the aid of churches and ducal administration as well as the timely death of France's king. Those circumstances and dynamics secured William's power, and he was able to accomplish the defeat of England by invading and landing his ships in Dives. There, William was met with Harold II on the battlefield, and the Battle of Hastings ensued in the fall of 1066. Bradbury asserts the Battle of Hastings events unfolded at Caldbec Hill, Battle Hill, or the Abbey in three phases. The first phase consisted of confrontation, with the Normans striking the Anglo-Saxons first. The second phase is a counterattack by the English. The third phrase consisted of a Norman breakthrough.
Without the treaty, there never would have been a Normandy formed. In fact, the assimilation of Vikings and their adoption of the French language and customs would have likely occurred in another time or another manner if at all.
The treaty eventually led to future power struggles between Normandy and England, such as the Norman Conquest. William II, Duke of Normandy, became William the I, King of England when he invaded England at the time of Harold II's reign in 1066. The Norman Conquest would cause native Anglo-Saxons, Danes, and the like to adopt the language that would eventually develop into Middle English.