Complex sentence: Inscriptions make it clear that he took the field in person against the rebels with his army in 133; he then returned to Rome, probably in that year and almost certainly--again, judging from inscriptions--via Illyricum.
Split into simpler sentences: Inscriptions make it clear that he took to the field in person against the rebels with his army in 133. He then returned to Rome, probably in that year and almost certainly--again, judging from inscriptions--via Illyricum.