Coins depicting Probus either with the Aegis chest piece or with the Aegis cloak Drawn after coins available online
The following quotes from Sextus Aurelius Victor and Eutropius are the best descriptions we possess of Probus as a soldier emperor and commander:
Probus… was almost a second Hannibal because of his great knowledge of warfare and versatile training of the soldiers and his toughening of the young recruits. [Aurelius Victor 37.2, tr. by H.W. Bird, p.41.]
Probus… a man rendered illustrious by the distinction which he obtained in war. He recovered Gaul, which had been seized by the Barbarians, by remarkable successes in the field. He suppressed, in several battles, some persons that had attempted to seize the throne, … He was a man of spirit, activity, and justice, equalling Aurelian in military glory, and surpassing him in affability of manners. [Eutropius 9.17, tr. by John Selby Watson, p.522.]
This and the descriptions of military action prove that Probus was a true master of warfare, who knew history and military science and how to use this knowledge for the benefit of the Roman Empire. However, he was not merely a bookworm, but an experienced veteran of several wars by the time he became emperor. It comes as no surprise therefore that he was the man who trained the most illustrious duces of the era, as was stated by Vopiscus (HA Probus 22.3). According to him, these men consisted of Carus, Diocletian, Constantius, Asclepiodotus, Hannibalianus, Gaudiosus, Ursinianus (Ursinus?) and others. In short, both Aurelius Victor and Vopiscus credit Probus with the improvements of the Roman forces that enabled them to secure the Empire in the coming years so that Constantine was able to launch a series of offensives to expand the Empire.
The military campaigns prove the above to be true. Probus always knew how to fight in the most advantageous manner regardless of the enemy, and he indeed defeated every type of enemy that existed. He was unfortunate in his choice of officers because he clearly should not have put any trust in their loyalty. Bonosus, Proculus, Saturninus and Carus all betrayed their master. It is impossible to say how much of this was his own fault. What is certain is that the strict discipline he instituted for the army did have its consequences just like it had during the reign of Aurelian. It is clear that his fame as a disciplinarian caused the Gallic usurpations. It is clear that his strict discipline improved the combat performance of the army, but at the same time it also caused the revolt that ultimately led to the murder of Probus. Both great soldier emperors, Aurelian and Probus, were killed because they were disciplinarians. In the case of Probus it is likely that he was primarily responsible for his own fate. In contrast, Aurelian was not directly responsible for the fate he suffered.
Of note is also the fact that Aurelius Victor compared Probus with Hannibal who was well-known for his merciless cruelty. Machiavelli (Prince, 17) claims that it was thanks to this cruelty that Hannibal was able to retain control of his soldiers, who never mutinied as a result. Indeed it is possible to think that Probus could have modelled his approach to the army after that of Hannibal and Aurelian; but if this is the case, then it backfired badly.
It is also clear that Probus made several mistakes in his military appointments because so many revolted against him. These men were undoubtedly able generals, but not worth the trust Probus placed in them. As noted by Kennedy (235–6), 1 if there was one fault in Probus, it was that he was too trusting towards his subordinates, especially Carus. There is no doubt that Probus was a good and loyal friend, but that some of his so-called friends betrayed this trust.
The reference to the personal interest of Probus in the training of soldiers and recruits suggests that he sought to make his army as versatile as possible. The idea was to make the Roman army suitable for all types of war that one could imagine, and on the basis of the military successes of Probus and his successors, he achieved his aim. The Roman army was prepared to meet any challenge the enemies threw at them. The reference to the training of soldiers and recruits also implies that Probus was the man who raised many of the units that appear during the so-called late Empire, which was after all only two years away at the time of his death. In short, Probus was the man who probably created the late Roman army which is visible to us only in the post-284 sources. He was the man who contributed most to the successes achieved by these forces. It is also very likely that the military equipment that is so familiar to us from this period was already standard issue during his reign so that all new units raised by him were equipped with it. The next emperor Carus wore the pilleus Pannonicus (round fur hat) with the implication that this had already been introduced as a standard piece of equipment.
On the civilian side of life, Probus’ greatest achievements were entirely based on his military successes. The most important of these was that he managed to keep the Empire together despite the centrifugal forces. It was thanks to this that he was able to make improvements in the economy, the most important of which was the growing of wine in Spain, Gaul, Pannonia and Moesia. This undoubtedly proved very beneficial for the economic wellbeing of all these areas. It was safer to drink wine than water and it was also a great service to all future generations who love to drink red wine as I do. In religion Probus was a traditionalist, but thanks to the fact that he did not launch any persecutions, society as a whole was united in plurality. The use of military forces for the persecution of religious or ethnic minorities when they did not pose any threat would have been a waste of resources and detrimental to the fabric of society. The fact that none of the sources mentions any conflict between Probus and the Senate means that Probus was also wise enough to avoid conflicts with the senators even if he still made it clear that he was deus et dominus whose decisions were not to be challenged. This means that he paid proper respect to the Senate and did not seek conflict with it. However, it is probable that the killing of Tacitus and Florianus was already sufficient as a precedent that the senators understood not to challenge his position which in turn meant that Probus had no need to chastise the Senate as had been the case under Aurelian.
In short, Probus would certainly deserve the title Great added to his name, but we should still not forget that his fame as a commander and his great military exploits were made possible by the efforts of Gallienus and Aurelian who formed the foundation for the rise of the Roman Empire back to the position it had held under Caracalla. It is clear that the three greatest military emperors of the third century after Caracalla were Gallienus, Aurelian and Probus – all operated in very different circumstances and all had different personalities, but all were great military leaders in their own ways. Also, all were killed by their own men just on the brink of their greatest successes. It was thanks to Gallienus, Aurelian and Probus that Constantine the Great became possible.
Coins depicting Probus either with the Aegis chest piece or with the Aegis cloak Drawn after coins available online
Bahram II (276-293) or Bahrain IV (388-399). Drawing by Ilkka Syvanne 2009.