Deal with the Devil: On The Bretons' Alliance with the Loire Vikings.
The Bretons realized that there was an opportunity to hire Viking mercenaries to fight the Franks, but at what cost?
History is rarely a story of permanent borders and ancient grudges; more often, it is a fluid game of musical chairs played by ambitious men. In the mid-9th century, the crumbling Carolingian Empire was the ultimate stage for this game. At the heart of the drama were two of the era’s most formidable “strongmen”: Robert the Strong, a rising star in the Frankish nobility, and Salomon, the ambitious so-called King of the rebellious Bretons.
Their relationship had begun as an alliance of opportunity, but ended in a bloodbath and Robert’s death at a village church at the hands of the Viking Hasting. The Breton/Frankish/Viking wars serve as the historical backdrop for my historical fiction series, The Saga of Hasting the Avenger, and are a central focus of my history book regarding the Vikings in Brittany.
The Rise of the New Guard
To understand the falling out between Robert and Salomon, we have to understand the world they inhabited. Following the bloody civil wars between the grandsons of Charlemagne, the old Frankish aristocracy had been decimated. In their place rose a new breed of military “meritocrats.”
Robert the Strong was the poster child for this pre-feudal social mobility. He wasn’t born into the highest echelons of power, but his martial brilliance made him indispensable to the Frankish King, Charles the Bald. Robert was a man who understood the value of land and the power of the sword. Charles, however, made a mistake with him. In attempting to settle the thorny question of Brittany, which had all but won its freedom from the Franks at the battle of Jengland, he made a deal with the Breton king Erispoë to marry his son Louis to Erispoë’s daughter Constance. Louis received the lands in and around Le Mans as a sort of dowry. But those lands already belonged to Robert.
It was during this period of fluid loyalties that Salomon—who seized the Breton throne by murdering Erispoë—and Robert found common ground. Together, they chased Charles’ son from Le Mans and forced him into an unfavorable peace treaty. In the ensuing peace negotiations, both men pledged themselves as fidelis (vassals) to Charles in exchange for territorial concessions. For Salomon, this was a way to keep trade routes open and settle domestic disputes while ostensibly appearing as a “loyal” subject of the Franks. For Robert, it was a way to regain his lands and standing.
The Cold War on the Breton March
The peace could not last. By 865, the political landscape shifted again. Charles and Robert reconciled, and the King handed Robert the keys to the kingdom: the Countship of Anjou and command of the March of Neustria.
This was a direct provocation to the Bretons. Robert’s new territory—previously known as the Breton March—was designed specifically as a buffer zone. Robert’s job was simple: keep the Bretons and the Vikings out.
Robert was perhaps the first Frankish commander who truly understood Breton tactics. As Salomon attempted to launch destabilizing raids into Neustria, Robert met them with disciplined force. For the first time, Salomon found himself boxed in by a man who was just as ambitious and militarily capable as he was. The “unruly vassal” was being tamed, and the rising Breton state faced an existential threat.
A Pact with the Northmen
Desperate to break Robert’s stranglehold, Salomon turned to an outside force that the Franks feared above all others: the Loire Vikings.
By the 860s, the “Northmen” were no longer just seasonal raiders; they were becoming a permanent fixture of the Loire River Valley. Having stripped the local monasteries and towns of their easy gold, these Vikings were looking for new ways to monetize their violence. They became the ultimate mercenaries.
Salomon struck a “deal with the devil.” He hired a massive warband of Northmen to strike Neustria from the south, catching the Franks off guard. Among the leaders of these Norse mercenaries was a figure who would become a legend of the Viking Age: Hasting.
While Hasting is the title character of my historical fiction series, The Saga of Hasting the Avenger, his historical presence is real and terrifying (though I haven’t quite made it to that stage of his life…yet). He represented a new kind of Viking commander who was interested in political leverage and sustained warfare as much as loot.
The Blood of Brissarthe
The escalation reached its breaking point in 866. A combined force of Bretons and Loire Vikings, likely under Hasting’s command, had just finished pillaging Le Mans and were retreating toward their ships. Robert the Strong, sensing an opportunity to end the threat once and for all, intercepted them at the village of Brissarthe.
The Franks forced the raiders into the village’s stone church. It should have been a total victory for Robert. The Vikings were trapped, surrounded by a superior Frankish force. But in the heat of the siege, Robert made a mistake.
Believing the Vikings were neutralized and exhausted by the heat, Robert and his men began to remove their heavy maille shirts and helmets to rest. It was the opening Hasting and his men needed. In a desperate, explosive sortie, the Vikings charged out of the church. Robert, caught unarmored and unprotected, was struck down in a doorway.
The Aftermath: A Kingdom Forged in Chaos
The death of Robert the Strong sent shockwaves through the Carolingian Empire. He was the “Shield of Neustria,” the only man capable of holding the frontier. With Robert gone, Charles the Bald’s defensive strategy collapsed.
In 867, at the Treaty of Compiègne, Charles was forced into a total diplomatic capitulation. He ceded the Cotentin Peninsula and the Avranchin to Salomon and—most importantly—officially recognized him as Rex: King of the Bretons.
Through his alliance with Hasting and the Norsemen, Salomon had achieved the largest territorial expansion of the Breton nation in history. He had reached the territorial zenith of his reign, but it came at a staggering cost. By inviting the Vikings into the heart of the empire to settle a grudge with Robert, Salomon had opened a door that would be nearly impossible to close.
Salomon had introduced a “people known for their barbarity and cruelty” into the very fabric of Breton life—a theme I explore in depth in my history book on the Vikings in Brittany. The Vikings were no longer just at the gates; thanks to Salomon, they were now part of the neighborhood.
If you enjoyed this deep dive into the bloody origins of the Breton Kingdom, be sure to check out The Saga of Hasting the Avenger for a fictionalized look at the man who killed Robert the Strong, or pick up my history of the Vikings in Brittany for the full account of these tumultuous years and their consequences.