While the Viking raids had been going on since the first half of 8th century, it is commonly agreed that the Viking Age started in 810 when the Danish king Gudfred the Great sacked the Frankish capital Aachen in a surprise attack, killing Emperor Karl the Cruel in the progress, and provoking a large scale revolt in Saxland.
Excerpt of “Vikings at War”
With the election of Gudfred, Daneland imported a much more aggressive outlook and one of his first actions as king was to break the agreement between his father Sigurd and Emperor Karl, and allowed Saxon to seek refuge in Danland once again. Karl found this unacceptable. He unexpectedly invited Gudfred for a peace conference in 804, and Gudfred saw this invitation as a sign of weakness and as an opportunity to brag to the emperor.
The king summoned a large part of his leiðangr as a show of force. A leiðangr was a naval-based military institution used to organize coastal fleets for seasonal expedition, in defense of the realm, large scale construction work and aggressive wars. Together with his hirð and leiðangr, Gudfred went to the future site of Hedeby south of the naval base Slesvig to meet the emperor as an equal. He had likewise a desire to receive Nordalbingia as a fief in return for a peace agreement as well as allowing to collect tributes from the Frisians.
However Karl had not invited Gudfred to the conference to restore a friendly relationship between them or find a solution to the border dispute. Instead he didn’t show up and sent Gudfred’s uncle Halfdan as envoy christianized during his time in the imperial court. Through his uncle, emperor Karl demanded the extradition of Saxon rebels and Christian slaves whom the Danes had taken with them from England and Frisia.
Nor did Karl want to place the border of his empire directly up against the territory of the Danes. Instead he turned Nordalbingia into a march and handed them over to the Obotrites as a reward for their service to the empire. Lastly Karl acknowledged no equal between the two monarchs and simply canceled the meeting. King Gudfred had lost face.
Gudfred was forced to act but he needed to wait four years as according to the leiðangr law, he could only raise a leiðangr every four years. He went on offensive in 808 and launched a punitive expedition against the Obotrites for daring to support the Franks before Karl the Younger pushed Gudfred back across the Eider river.
The invasion was successful in spite of considerable Danish losses, and Gudfred demanded tribute from the Obotrites. Before returning home, Gudfred destroyed the important tradeport Reric by the Baltic coast and forcibly relocated its merchants, craftsmen and their families to south of Slesvig, where he established Hedeby. Hedeby soon took over Reric as the center of trade between east and west over the narrow southern part of Jutland.
Fearing Frankish reprisals, Gudfred put his leiðangr to expand and strengthen the fortifications along the border known as Danevirke, as well as construct earthwork around Hedeby and connect with the rest of the main fortification. The improved Danevirke ran from the Schlei toward the west coast of Denmark along the river Treene.
At the same time, emperor Karl called for an imperial assembly in Thionville in 806 in order to make a last will and testament. He declared the partition of his empire into three autonomous realms along linguistic and cultural boundaries. This was meant to ensure the loyalty of the local population in territories freshly conquered as well as ensure a balance of power between the three realms. The crowns of the three realms were given to his sons.
The testament which emerged from the assembly was lost to time but the division of the revived Roman Empire was clear. The empire was divided in North Francia, West Francia and South Franca in a roughly north-southwest-southeast configuration and established a political framework which came to dominate the continent for the coming centuries.
As his sons were already rulers of their respective realms, it was only a matter of confirming their kingships. For his eldest son Karl the Younger, he designated Austrasia, Neustria, Frisia, Saxony, half of Burgundy, and half of Alamannia. To Pippin Carloman, he gave Italy, Bavaria and the other half of Alamannia. Louis the Pious would receive Aquitaine, Provence, the other half of Burgundy and the Spanish March.
However the imperial title was not mentioned as Karl regarded the title as an honorary achievement that held no hereditary significance. Neither was the division seen as a division of the empire, but as a division of power within the royal family.
The Imperial princes, now kings of North Francia, West Francia, and South Francia, returned to their realms, while the Roman Emperor returned to Aachen where he stayed for the remainder of his life and focused on theological matters.
Emperor Karl had hoped this imperial decree would ensure peace and stability in his empire with an orderly succession to his sons upon his death, but little did he know that his aggressive conquest of Saxony had stirred up a hornets’ nest.
Over the next couple years, both Gudfred and Charlemagne tried to find a diplomatic solution to the border dispute through emissaries, but it did not lead to any concrete agreement. The relationship between the two monarchs hit bottom in 810, and the question was now not about whether it would be possible to reach an agreement, but who would attack first.
As the storm was brewing, the pro-Frankish faction within Gudfred’s court had not forgotten the events in the Saxon Wars and still feared that their king’s ambitions would bring the wrath of the emperor upon them. They and the children of Halfdan, who had returned from the court of emperor Karl with a promise of support from said emperor, plotted a conspiracy against their king.
Just as Gudfred prepared to assemble his leiðangr, his nephew Hemming stepped forward and declared Gudfred to be unfit to rule. He claimed Gudfred was a mad king thinking he could defeat the might of the greatest empire since the time of the Romans. That the honorless king was stuck up in a vain hope that he would win such a war, which only will bring doom to the Danes. Hemming challenged the king to hólmganga, which Gudfred was forced to accept, as refusing was considered to be a lack of honor..
Of course the Danes might have misjudged the situation as the Franks proved not to be omnipotent and emperor Karl had to run all over places to keep his overstretched realm in check. Nonetheless both Heming and Gudfred settled down for a ritualist trial by combat and the crown of Daneland was the prize.
After the terms were set, the duel began three days after the challenge had been given on a constructed ring surrounded by witnesses and moderators. Under the eye of Óðinn, the combatants fought on using sword and shield until the first blood was spilled. When the duel came to an end, a bull was slaughtered to please Óðinn. Despite his young age, Herming grew up as a decadent prince in emperor Karl’s court, and he was outmatched by the vast more experienced Gudfred.
Victoriously Gudfred resumed his plan of attack against emperor Karl without resistance from his court as Óðinn clearly stood on the side of the king.
This was when Karl sat in his palace at Aachen and plotted an expedition against Gudfred, that he received a proclamation stating that Gudfred had attacked first. Gudfred had raised a large host of around 6,000 men and 200 longships.
The Danish host landed on Frisia, and routed the local garrisons after three battles. but not before ravaging the isles off the coast. To add further insult, king Gudfred demanded tributes from Karl’s subjects. According to the latest report, the Danish fleet was not far away from Aachen, the capital of the Frankish empire.
Hearing this, the incensed emperor forcibly conscripted whatever peasants he could find and ordered the establishment of a camp at the confluence of Aller and Wesser, so he could await Gudfred there. He hoped that the Danish king was too arrogant and wanted to fight the emperor on the open field with his horde of unruly barbarians on a mushroom trip.
Unfortunately, the Franks had vastly underestimated the Danes and believed they fought the same way as the Saxons and they had only faced the followers of Óðinn in the Saxon Wars, and not the professional leiðangr army. Both the hirð and the leiðangr were in no way some unruly barbarians on mushroom trips, but rather highly disciplined marines.
Unlike their mainland cousins, the Norsemen had developed a military doctrine of rapid maneuver warfare, utilizing the advantages of their longships to a great extent. With the longships, the Norsemen could attack unexpectedly and quickly with the moment of surprise on their side, only to disappear as fast as they came. Besides some few annoyed raids in the past decades, the Franks had not yet developed a counter against this kind of warfare.
Prior to the attack on Aachen, a thorough reconnaissance of terrain, and the location of the camp was carried out. The Franks never discovered that the Danish fleet had skipped the vanguard in cover of darkness and sailed to Aachen undetected. The fleet landed near the city on a landing site pointed out by their scouts at twilight.
To the horror of the emperor, the Danish warriors stormed the city led by King Gudfred himself. The king occupied the palace of Aachen and supposedly dueled the emperor himself before being caught. He was hanged and stabbed with a spear as an offering to Óðinn and was sent down to Valhalla. According to questionable sources, King Gudfred and his warriors slayed all members of Karl’s family as well as his court who was at present in the palace as a vengeance for the Massacre of Verden in 782.
Both the city, the palace and the cathedral as well as several churches within the city were pillaged. Gudfred’s army left the sacked city before frankish reinforcements could arrive but not before setting the palace on fire. Among the imperial and cathedral treasures, the king collected religious tokens and texts which had been stolen by Emperor Karl from religious sites in Saxland
News of the sacking of Aachen and Karl the Great suffering a martyr dead in the hand of heathens spread quickly through the Frankish empire and chaos ensued. His death divided the empire between his three sons, according to Divisio Regnorum, a division plan issued by Karl the Great in 806.
King Gudfred reinforced his tribunal overlordship over the northern Frisian provinces before returning victoriously home to Daneland. The sack had completely sidelined the anti-frank faction, especially the returning of holy relics and texts from Saxland and the death of the Emperor. A massive runestone was raised at his royal seat in Lejre in memory of his victory against the Franks:
“King Gudfred ordered this monument made in memory of Sigurd, his father, and in memory of his victories, that Gudfred won for himself all of Daneland, vanquished Imperator Karl the Cruel and avenged the souls at Venden.”
Many tribes which inhabited the frontiers of the Frankish empire were once in awe of Karl’s power and had until now dared not to stir up any trouble. However they now began to stir up, as the death of Karl the Great had proved that the Franks were not invincible. Some looked towards Gudfred hoping that he would help them in throwing the Frankisk yolk off. One such tribe was the Saxons.
