Probus served as a tribune under Aurelian, Tacitus, and Florianus. He proved capable, so Tacitus appointed him governor in the east. When Tacitus died, his brother, Florianus, assumed the imperial purple. However, Probus followers declared their guy emperor. Probus defeated Florianus and spent his rule fighting barbarians. The emperor was wary of the military and kept them busy doing make work projects. In the end, they despised the work and assassinated Probus.
Emperor Tacitus died leaving Florianus in charge. Governor Marcus Aurelius Probus claimed Tacitus had named him, and not Florianus, his successor. Probus claim is doubtful since most emperors attempted to establish family dynasties. Either way, the army lost confidence in the emperor and removed him. Probus assumed power upon Florianus' assassination.
The new emperor marched to Rome, was confirmed by the Senate, and then marched to the frontiers. Probus spent the bulk of his reign fighting barbarians. Germans poured over the Rhine leading to a two year campaign. In 278, Probus defeated the Vandals. The next year, he put down an insurrection. In 280, he eradicated rebellions in Gaul and Germania.
Probus defeated barbarians and usurpers alike. In 281, he celebrated a triumph in Rome. Additionally, the emperor initiated a policy of settlement for barbarian tribes. He settled over 100,000 within imperial borders in an attempt to pacify the invaders. This policy had far reaching consequences as future emperors followed the precedent. Afterward, Probus decided to keep his army busy to avoid potential insurrection or rebellion.
An army is designed to fight and many Roman emperors discovered an idle military is a dangerous one. As a result, Probus ordered the soldiers to work on building defenses, bridges, buildings, drain lands, and plant vineyards. The legions resented planting vines and morale dangerously dropped. The armies in the Upper Danube declared praetorian prefect Carus the new emperor and revolted. Many defected to Carus, who apparently did not want to be emperor, but had little choice. The defections went from a trickle to a tidal wave and Probus' own troops switched sides. They murdered the emperor in 282.
Probus successfully campaigned against usurpers and barbarians alike. He initiated a settlement policy designed to placate barbarian invaders which future emperors followed. However, his determination to keep the army busy to deflect their energies away from assassination failed. They resented the busy work and murdered the emperor.