Prelude After the Frankish conquest of the Kingdom of the Lombards, Francia became the Avars' sole western neighbour but the tradition of Avar–Lombard alliance allegedly survived.
Aio, a leader of an unsuccessful Lombard rebellion against Charlemagne fled to the khaganate in 776. By the 780s, Bavaria remained the last autonomous duchy in Francia, and Charlemagne decided to subjugate it. He forced
Duke Tassilo III () to repeat his oath of allegiance to him at
Worms in 781. Next summer Avar troops were assembling on the Enns, but they did not cross the river. Instead, an Avar delegation went to
Lippspringe to start peace negotiations with Charlemagne but he only "heard and dismissed" the Avars. When Tassilo failed to obey Charlemagne's summons to attend an assembly at Worms in 787, Charlemagne invaded Bavaria, forcing Tassilo into submission. A year later, at an assembly in
Ingelheim, Bavarians who were loyal to Charlemagne accused Tassilo and his Lombard wife
Liutperga of conspiring with the Avars. They were found guilty and Tassilo was deposed. The historian
Walter Pohl states that even though "the sources reflect Frankish propaganda, it is possible that a Bavarian–Lombard coalition of the defeated sought, with Avar help and Byzantine backing, to check Charlemagne's triumphal advance".
Avar attacks Charlemagne's biographer
Einhard (d. 840) says that aside from "the
war against the Saxons, the greatest of all the wars waged by [Charlemagne] was the one against the Avars" in 791. According to Einhard's account, the war started in 788. Bavaria's full integration in Charlemagne's realm alarmed the Avars. They attacked northern Italy and Bavaria, but both armies were defeated. In retaliation for the invasions, two Bavarian commanders, Graman and Otachar led troops across the Enns and routed the Avars on the plains along the river
Ybbs. The Avars launched a new invasion of Bavaria, but they were again defeated and many of the Avars fleeing from the battlefield drowned in the Danube. The khagan sent envoys to
Worms to start negotiations about the borders. According to Pohl, the Franks probably wanted to seize lands across the Enns, but the Avars refused.
First Frankish campaign (left) and his son,
Pippin of Italy (right) Charlemagne came to
Regensburg to make preparations for an invasion of the Avar Khaganate in early summer 791. The
Royal Frankish Annals notes that the war was justified by the "excessive and intolerable outrage committed by the Avars". In preparation for the campaign, troops from Austrasia and Neustria assembled at Regensburg together with Saxons,
Frisians,
Ripuarian Franks, Thuringians, Alamanni and Bavarians. Charlemagne's younger son
Louis came from Aquitania. He ordered his eldest son
Pippin,
King of Italy (), to lead a —a highly mobile military unit—against the khaganate. This strike force reached Avar territory (probably the region between the rivers
Drava and
Sava) in August. They routed the Avars, pillaged an Avar fortress and seized much booty and 150 captives before returning to Italy. Charlemagne divided the main army into two parts. He appointed one of his relatives, Count Theoderic, and the
chamberlain Maginfred to be the supreme commanders of the contingents of the Ripuarian Franks, Frisians, Saxons and Thuringians, and kept the rest of the Frankish troops along with the Bavarians and Alamanni under his own command. A fleet was also built for the Danube. His campaign started only after the end of the harvest season. The two armies marched along the two banks of the Danube but a later version of the
Royal Frankish Annals indicates that at least part of the northern army marched through southern
Bohemia. The historian Charles Bowlus proposes that the destruction of the Avar fortifications in the borderlands was Charlemagne's principal strategic purpose because as long as they existed the Franks were unable to make raids into Avar territory. Before invading the Avar territory, the two armies pitched camp at Lorch near the frontier early in September. Clergymen accompanying the army ordered fasting to win divine favor on 5 September, although Charlemagne was reluctant to fast, according to his biographer,
Einhard (d. 840). For three days, the consumption of meat was prohibited and the amount of the wine available to soldiers was limited. The clergy were singing
psalms and reciting
litanies, and each priest was required to say a
mass. The army set off for Avar territory after one week or two, presumably when news about Pippin's victory reached the camp at Lorch. On learning of the Frankish invasion, the Avars abandoned their fortresses at the confluence of the river Kamp with the Danube and at (near present-day
Krems an der Donau and
Tulln an der Donau, both in Austria, respectively) without much resistance. The fortress at Kamp was seized and destroyed by Maginfred. At , Charlemagne's thirteen-year-old younger son,
Louis was gilded with sword for the first time, but he soon returned to Francia. The Franks continued their invasion reaching as far as the river
Rába. Here, according to a later version of the
Royal Frankish Annals, a pestilence broke out in Charlemagne's camp killing about 90% of their horses. The historian Carroll Gillmor identifies the pestilence as
Eastern equine encephalitis, a contagious disease spread by mosquitos. Pohl argues that it is "very likely that the disease had already affected the Avar horses, which may explain why the Franks encountered no resistance" during the campaign. Charlemagne was to abandon the campaign in the middle of October. His army returned to Bavaria via (now
Szombathely in Hungary), while Theoderic and Maginfred led their troops across Bohemia. The states that Charlemagne's campaign lasted for 52 days. It was considered a significant military action: some charters issued at
Freising were dated in reference to the campaign's year. At least two bishops—Sindpert of Regensburg and
Angilram of Metz—died during the campaign but due to illness, not fighting the Avars.
Interval After concluding the campaign, Charlemagne returned to Regensburg. He stayed in Bavaria in 792 and most of 793, although he faced serious problems in other parts of his empire, including a new uprising in Saxony and the rebellion of his illegitimate son
Pepin the Hunchback (d. 811). Charlemagne's enemies noticed his preoccupation with Avar affairs. The Saxons sent envoys to the Avars to forge an alliance, and the
Moors of
Al-Andalus, or Muslim Spain, expected that the Avars would tie down Charlemagne's military forces in Central Europe. He did not launch new military campaigns in 792. Gillmore attributes Charlemagne's inactivity to the shortage of trained warhorses after the equine epidemic. Charlemagne was preoccupied mainly with logistical projects in 792 and most of 793. He ordered the construction of portable bridges to facilitate river crossing. In 793, Charlemagne sent to raid Avar territory. He left Regensburg for a new invasion of Avar territory but the Saxons rebelled and defeated Count Theoderic. After learning of the Saxons' victory, Charlemagne abandoned the military campaign. He decided to build a canal linking the Rhine and the Danube. A navigable canal could have eased the movement of troops and supplies towards the khaganate but he abandoned this ambitious project by the end of the year. Meanwhile, a civil war broke out in the Avar Khaganate, likely not independently of the permanent Frankish pressure. During the conflict, the khagan and another Avar leader, the were murdered by their people. A third Avar leader, the
tudun sent envoys to Charlemagne's camp near the Elbe and offered his subjection to the Frankish king.
Sack of the "ring" , likely an Avar treasure Taking advantage of the internal conflicts in the khaganate, Duke
Eric of Friuli mustered troops for a surprise attack against the Avars in 795 or 796. Instead of leading the risky operation in person, he appointed the Slav
Woynimir to command it. Bowlus proposes that Woynimir was a South Slav leader, while Pohl thinks that he was an ambitious Slav warrior in Frankish service. Woynimir led his troops as far as the khagan's residence, known as the "ring" and located likely in the plains between the Danube and the Tisza. Pohl argues that the khagan's seat was "most likely a fixed palace settlement, laid out in a circle, with tents or wooden structures". Woynimir sacked the "ring" and seized much of his impressive treasure as booty. After Woynimir's return to Friuli, Duke Eric sent the booty to Charlemagne who gave part of the treasury to the pope.
Second Frankish campaign Pippin of Italy and Eric of Friuli gathered troops for a new invasion of the Avar Khaganate in 796. Charlemagne sent Bavarian and Alamannian reinforcements to join his son's campaign. Bowlus proposes that the Bavarians followed the route that Charlemagne had taken in 791, while the Alamannians crossed the Alps via the
Brenner Pass to reach Avar territory. The Italian, Bavarian and Alamannian armies united in Lower Pannonia. They met no resistance while they were marching towards the Danube. The khagan, who had assumed power after the civil war, approached Pippin on the Danube accompanied by his wife and Avar dignitaries, including the katun and tarkhans. A contemporaneous panergy, ("King Pippin's victory over the Avars"), states that an Avar named Unguimeri had convinced the khagan to submit to the Franks without resistance. The Avars who refused the khagan's reconciliatory policy withdrew to the lands to the east of the Tisza. Pippin crossed the Danube and seized much booty at the "ring" before destroying it. After his victory, Pippin held a synod on the Danube to make arrangement for the Christianization of the Avars. Under the direction of Patriarch
Paulinus II of Aquileia (d. 802/804), the assembled clerics decided that the Christians who had lived under Avar rule were to be rebaptized only if untrained clerics had baptized them. ==Notes==