Firmus (4th-century usurper)
Firmus was the son of the Moorish (Berber) prince Nubel, a powerful Roman military officer, as well as a wealthy Christian. When Nubel died, Firmus killed his half-brother Zammac, who illegitimately had appropriated of Nubel's wealth, and become successor to his father.
Between 372 and 375, Firmus revolted against the comes Africae Romanus, who was a supporter of Zammac. The misbehaviour of Romanus, who had neglected protection from African tribes to Roman cities that had refused the payment of bribes, had worsened the situation in Africa Province in 360s. The revolt of Firmus against Romanus forced Valentinian to take action against both his officer and the African rebel.
When Valentinian sent his magister militum Theodosius (father of Theodosius I) to depose Romanus, Firmus tried to find a compromise with him, but Theodosius refused peace to Firmus, who had proclaimed himself emperor.
With the support of the indigenous African tribes, Firmus obliged Theodosius to a bloody and hopeless campaign. In the end, however, Firmus was betrayed by one of his supporters, and chose suicide over capture.
- Roberts, Walter, "Firmus (ca.372-ca.375 A.D.)", De Imperatoribus Romanis site