Conflict between the Illyrians and Romans started in 229 BCE, but Rome did not complete its annexation of the region until AD 9. It was precisely in modern-day Bosnia and Herzegovina that Rome fought one of the most difficult battles in its history since the Punic Wars, as described by the Roman historian Suetonius. This was the Roman campaign against Illyricum, known as ''Bellum Batonianum''. The conflict arose after an attempt to recruit Illyrians, and a revolt spanned for four years (6–9 AD), after which they were subdued. In the Roman period, Latin-speaking settlers from the entire Roman Empire settled among the Illyrians, and Roman soldiers were encouraged to retire in the region.