During the
Frankish war against Avars, the
Royal Frankish Annals made mention of a
Wonomyrus Sclavus (Vojnomir the Slav or Zvonomir the Slav) active in 795.
Eric, Duke of Friuli, sent Vojnomir with his army into Pannonia, between the
Danube and
Tisza, where they pillaged the Avars' dominions. The next year the Avars were defeated and Frankish power was extended further east, to the central Danube. In the mid-9th century, Lower Pannonia was already inhabited by a Slavic majority (besides "Pannonian Slavs" including
Dulebes and possibly some
Croats), and Christian Avars were also found in Lower Pannonia in 873. After the destruction of the Avarian state, Pannonian Slavs came under Frankish rule. Initially, local Slavic princes were under Frankish suzerainty, within the
March of Pannonia, and some of them are known from Frankish primary sources. Prince
Ljudevit was mentioned in the
Royal Frankish Annals as
Duke of Lower Pannonia (), having led an uprising against the Franks (811–822). Their motives aren't known but it's presumed to have been led by the desire for greater autonomy. He was joined by the
Carantanians,
Carniolans, reportedly Slavs around
Salzburg and was supported by (
Patriarch of Grado) - which was a substantial threat as their strength partly mirrored the former Avar Khaganate. His stronghold was in
Sisak (), former metropolis of ancient Roman province
Pannonia Savia. However, the exact boundaries of his principality are uncertain as the term of Lower Pannonian could have implied both the lands between the river
Drava and
Sava as well as north of them and east of them in the former Roman province
Pannonia Secunda (today's
Syrmia). Possibly his rule expanded further to the east because in the historical sources is said to have been joined by the tribe of
Timočani who lived around
Timok Valley (in today's eastern Serbia). The size of the principality had to be proportional to the resources needed to rebel against the military forces of
Borna of Dalmatia and Franks. After Ljudevit's failed uprising and death, in 827 the
Bulgars under Great Khan
Omurtag invaded and conquered Lower Pannonia and parts of Frankish territories to the north. They also installed their own governors. The Bulgarian-Frankish conflict was probably spurred over the control of the tribes of Timočani and
Abodrites. German King
Louis in 828 made a counterattack and eventually
March of Friuli was divided into four counties. One of them probably was early
Duchy of Croatia (which also expanded upon the territory of Sisak) while Pannonia again became part of the Pannonian March, both of which vassals to
East Francia. The next year Bulgars made another attack but without further success, although the territory of Pannonia most probably lost its eastern part to the
First Bulgarian Empire. After that, in 838 a local Slavic prince
Ratimir emerged as the new ruler in Lower Pannonian regions, around rivers Drava and Sava. He probably ruled the eastern areas of Pannonia and was a Bulgar's governor. To him fled
Pribina, former prince of the
Principality of Nitra expelled by
Mojmir I of Moravia. In the same year Frankish count
Radbod of the East March deposed Ratimir and strengthened Frankish rule in Lower Pannonia. Ratimir fled the land, and the Franks instated Slavic prince Pribina as the new ruler of Lower Pannonia. Pribina (d. 861) was succeeded by his son, prince
Kocel. During the rule of Pribina and Kocel, capital of the Principality of Lower Pannonia was Mosapurc (
Mosapurc regia civitate), also known in
Old-Slavonic as
Blatnograd (modern
Zalavár near
Lake Balaton). The polity was a vassal
principality of the Frankish Empire, or according to others, a frontier
county () of the
Eastern Frankish Kingdom. It was initially led by a
dux (Pribina) and later by a
comes (Kocel) who was titled as "
Count of the Slavs" (). Their authority stretched towards the northwest up to the
Rába river and
Ptuj, and to the southeast up to the
Baranya region and the Danube river. During the time of Kocel, Byzantine missionary
Methodius was active in Lower Pannonia, and to the same period is dated
Pope John VIII's letter to uncertain
dux Mutimir, commonly considered to be
Mutimir of Serbia, about the formation of the
Diocese of Pannonia with the seat in
Sirmium and which archbishop at Kocel's request was Methodius (see also
Archbishopric of Moravia). The course of events by the end of the 9th century is unclear. Although still under the Frankish influence, a new threat was coming from
Svatopluk I of Moravia.
Braslav was the last
dux of Lower Pannonia between at least 884 and 896. ==Aftermath==