In the summer of 791, after unsuccessful peace negotiations, Charlemagne invaded the khaganate along the river Danube from the west, while his son King Pippin of Italy (r. 780–810) attacked from the southeast.

Charlemagne's troops destroyed two Avar fortresses across the Enns River but an equine epidemic killed about 90% of his horses, forcing him to abandon the campaign.

Taking advantage of an Avar civil war, Duke Eric of Friuli (r. 789–799) dispatched a highly mobile military unit to the khaganate under the command of the Slav Woynimir in 795 or 796.

The Franks emerged from a loose confederation of Germanic tribes dwelling along the lower course of the river Rhine during the Late Roman period.

The Franks conquered Burgundy, Provence, and the Alpine region, and subjugated the neighboring Germanic tribes—the Thuringii, Alemanni and Bavarians.

The Merovingian kings had direct control over the lands between the rivers Loire and Rhine but the peripheries of Francia were governed by virtually autonomous rulers, among them the Agilolfing dukes of Bavaria.

[2] Fleeing from the expansion of the First Turkic Khaganate in Central Asia, the Avars appeared on the European political scene in early 558.

[3][4] Justinian accepted the offer, and the Avars—reportedly 20,000 mounted warriors—continued their westward migration and conquered the Turkic and Slavic tribes in the Pontic steppes.

Early next year, the Lombards voluntarily abandoned the Basin's western region for northern Italy, and the Avars took possession of all the plains along the Middle Danube and its tributaries.

[13] Around the same time, an Avar succession crisis ended with the flight of 9,000 Bulgar warriors and their families to Bavaria where many of them were massacred on the orders of Dagobert I of Francia (r. 623–639).

[14] Samo's realm fell apart after his death and archaeological evidence indicates the Avars' westward expansion along the Danube in the second half of the 7th century.

When Bishop Emmeram decided to leave for a proselytising mission to the khaganate, Duke Theodo of Bavaria (r. 670/680–715) dissuaded him because of an armed conflict along the frontier.

An aristocratic family, later known as Carolingians, assumed real power as the hereditary holders of the important office of mayor of the palace.

[19] In 751, the Carolingian Pippin the Short (r. 751–768) deposed the last Merovingian rule Childeric III (r. 743–751) and assumed the title of king in 751.

[20] 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.

[22] 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.

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".

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.

[29] The Royal Frankish Annals notes that the war was justified by the "excessive and intolerable outrage committed by the Avars"[citation needed].

[28] In preparation for the campaign, troops from Austrasia and Neustria assembled at Regensburg together with Saxons, Frisians, Ripuarian Franks, Thuringians, Alamanni and Bavarians.

The historian Carroll Gillmor identifies the pestilence as Eastern equine encephalitis, a contagious disease spread by mosquitos.

[36] 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.

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.

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.

[39] 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.

[46] Pohl argues that the khagan's seat was "most likely a fixed palace settlement, laid out in a circle, with tents or wooden structures".

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 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.