Well, he was really just one of a line of soldier-emperors in what is sometimes called the "military chaos" period of the Roman empire. The empire was under severe pressure from barbarians along the Rhine and Danube and from the Sasanian (Persian) empire in the East, and had started to fragment. An emperor named Claudius (not the one from the BBC series, this is 200 years later) started a reversal in fortune by annihilating a Gothic army in the Balkans and earning himself the name Claudius Gothicus, but he then died of the plague. A general named Aurelian became emperor and proceeded to recover Gaul (France), Britain, Egypt, and Syria for the empire and expel barbarians from Italy in a series of brilliant campaigns. He defeated the Palmyrene empress Zenobia, and the showdown between the tough old Roman general and the cunning Eastern beauty has fascinated historians ever since.
Aurelian was murdered by his own staff, and the top general in the East, Probus, seized power. The situation in the empire was still chaotic, and Probus was able to restore it mostly to tranquility in his reign from 272-282AD. He is most famous for completely expelling barbarians from Gaul and even taking the fight across the Rhine and Danube to the barbarian homelands. He also annihilated invaders in Egypt and intimidated the Sasanian shah into a favorable peace (some sources claim there was a battle). While preparing for a massive attack on the Sasanians, he put the soldiers to work on public works projects, which they hated, and also spoke of being able to disband the armies to save the people a great expense after this last campaign.
This was a bit much for the army, and the praetorian prefect (commander of the bodyguard) Carus was able to exploit the situation and have Probus murdered. The Romans were still itching for revenge against the Sasanians, who had captured and eventually killed an earlier Roman emperor named Valerian, and Carus took advantage of Probus' preparations and invaded Mesopotamia (this is the campaign the story comes from). The Sasanians were busy with a civil war, and Carus easily took the Sasanian capital of Ctesiphon. He then died under very mysterious circumstances...the historians say he was struck by lightning, which was a very bad omen to the Romans, a sign that Jupiter was angry.
These men were very different from the early Roman emperors in that they were not aristocrats...the military challenges of the period led to the strongest generals forcing themselves into the position of emperor, instead of a more polite succession being arranged through the Senate ahead of time by the previous emperor. The generals themselves had to be Senators in the early empire, but that had also been abandoned in favor of the best soldiers being promoted while the aristocrats stayed in Rome and enjoyed their wealth.
If you ever read "The Decline and Fall of the Roman Empire" by Gibbon or the somewhat bogus "Augustan History" from ancient time, you will see that Probus is made out the be the true hero of the recovery of the empire, the best and most virtuous emperor of his time. Aurelian probably really deserves most of the credit for the recovery, though. I became interested in Probus through coins...his are relatively inexpensive and much more interesting than most of that period, with very fancy busts of the emperor wearing different military and consular outfits. He seemed to be trying to project an image of himself as a strong military man who also respected the traditions of the empire. "Probus" is actually a Latin word roughly meaning honest, upright, fair, and the English word "probity" derives from it. The Latin historians were fond of saying that Probus was, indeed, a man of probity.
There is an excellent bust of Probus in the Capitoline Museum by the Forum...you can't touch it, though, I got in trouble for that.
http://en.museicapitolini.org/percorsi/per...tratto_di_probo