Following the completion the Parthian campaign, Emperor
Marcus Aurelius appointed him
military governor of
Pannonia Inferior on the empire's northern frontier along the
Danube River. He likely served from 164 until 168. In late 166 or early 167, a force of 6,000
Lombards invaded Pannonia. Pompeianus defeated the invasion with relative ease, but it marked the beginning of a larger barbarian invasion. Late in 167, the
Marcomanni tribe invaded the empire by crossing in Pannonia. Marcus Aurelius and Lucius Verus planned a punitive expedition to drive the barbarians back across the Danube River, but due to the effects of the
Antonine Plague, the expedition was postponed until early 168. Aided by Pompeianus, the two emperors were able to force the Marcomanni to retreat. Pompeianus' military skills earned him the confidence of Marcus Aurelius and he quickly became one of the Emperor's closest advisors. As the emperors returned to their winter quarters in
Aquileia, Lucius Verus fell ill and died in January 169. Marcus Aurelius arranged for his daughter
Lucilla, Verus' widow, to marry Pompeianus. As son-in-law to the emperor, Pompeianus became a member of the
Nerva–Antonine dynasty. The emperor even offered to name Pompeianus
Caesar and his heir, but Pompeianus declined the title. Instead, Pompeianus was promoted and served as the emperor's chief general during the Marcomannic War. Under his guidance, the exiled senator and fellow Parthian war veteran
Pertinax was recalled and joined Pompeianus on his military staff. Pompeianus' successes during the Marcomannic War further distinguished him, with the emperor awarding him a second consulship in 173. He took part in a number of military operations in the Danubian region and was still stationed in the region following the death of Marcus Aurelius. ==Under Commodus==