Illyrian Warfare - Great Illyrian Revolt

The Great Illyrian Revolt, (Bellum Batonianum or Pannonian Revolt) was a major conflict between an alliance of Illyrian communities and the Roman forces that lasted for four years beginning in AD 6 and ending in AD 9. In AD 6, several regiments of Daesitiates, natives of area that now comprises central Bosnia and Herzegovina, led by Bato the Daesitiate (Bato I), were gathered in one place to prepare to join Augustus's stepson

and senior military commander Tiberius in a war against the Germans. Instead, the Daesitiates mutinied and defeated a Roman force sent against them. The Daesitiates were soon joined by the Breuci led by Bato of the Breuci (Bato II), another community inhabiting the region between the rivers Sava and Drava in modern Croatia. They gave battle to a second Roman force from Moesia led by Caecina Severus (the governor of Moesia). Despite their defeat, they inflicted heavy casualties at the Battle of Sirmium. The rebels were now joined by a large number of other communities. At risk was the strategic province of Illyricum, recently expanded to include the territory of the Pannonii, an indigenous communities inhabiting the region between the rivers Drava and Sava, who were subjugated by Rome in 12–9 BC. Illyricum was on Italy's eastern flank, exposing the Roman heartland to the fear of a rebel invasion.

Augustus ordered Tiberius to break off operations in Germany and move his main army to Illyricum. Tiberius sent Marcus Valerius Messalla Messallinus (the governor of Dalmatia and Pannonia) ahead with troops. The panic broke out in Rome and Augustus raised a second task force under Tiberius's nephew Germanicus. He resorted to the compulsory purchase and emancipation of thousands of slaves in order to amass enough troops. This happened for the first time since the aftermath of the Battle of Cannae two centuries earlier. At one moment, in winter AD 6/7, 10 legions were deployed and an equivalent number of auxilia (70 cohors, 10 ala and more than 10,000 veterans). In addition, they were assisted by a large number of Thracian troops deployed by their King Rhoemetalces I, a Roman amicus ("ally") a grand total of some 100,000 men.

They faced further reverses on the battlefield and a bitter guerrilla war in the Bosnian mountains, but bitter fighting also occurred in southern Pannonia around Mons Almus (modern Fruška Gora) near Sirmium. It took them three years of hard fighting to quell the revolt, which was described by the Roman historian Suetonius as the most difficult conflict faced by Rome since the Punic Wars two centuries earlier. Tiberius finally quelled the revolt in AD 9. This was just in time: that same year Arminius destroyed Varus's three legions in Germany. The Roman high command did not doubt that Arminius would have formed a grand alliance with the Illyrians.

The fighting of the Illyrian Revolt had lasting effects on Roman soldiers. Unhappy with their payment of swampy and mountainous Pannonian lands for such harsh military service, and with abuses relating to their pay and conditions, Roman soldiers staged a mutiny in AD 14 demanding recompense. Tiberius dispatched his son, Drusus, to pacify the mutineers.