Whether it was his annoyance at not being able to close the doors to the temple of Janus or more likely in retribution for the Dacian crossing of the Danube in 10 BC, Augustus mounted a military campaign against the Dacians, apparently sending at least two generals into action. The Dacians, although nowhere near the threat that they had been when unified under Burebista, had demonstrated a continued willingness to become involved in areas that Rome deemed under her area of influence. Although it seems clear that this was not intended to be a war of conquest, the fact that it is mentioned in his memoirs demonstrates the importance of these campaigns and the spin that he hoped to apply to these events.
Unfortunately, very little is known about these campaigns and no clear record of what took place is extant. What little is known is that Marcus Vinicius was sent to deal with the Dacians and the Bastarnae after the Dacian crossing of the Danube in 10 BC. What is recorded in the sources is that Vinicius managed to defeat an army of Dacians and Bastarnae and then forced the Celtic people living on the Great Hungarian Plain to ally with Rome. This suggests that Vinicius’s focus was on the plains and lowland areas, whereas according to Florus another general, Cn. Cornelius Lentulus, who was also active against the Dacians in this period, seems to have concentrated on the highland Dacians. Lentulus’s forces apparently sailed up the Tisza and Maros rivers before entering the mountains to reach the Dacians. Although there is some debate as to when exactly Lentulus’s campaigns north of the Danube occurred, it is a reasonable assumption that they were an element in the retaliatory actions against the Dacians for the crossing and attack of 10 BC.
Another argument for the date of Lentulus’s campaigns is that if Tiberius did in fact defeat the Scordisci in 14 BC immediately after his Alpine campaigns, then it may also have been that year which saw Lentulus cross the Danube and attack the Dacians, although this is conjecture and far from certain. Perhaps the most significant issue with a date of 14 BC is that it precedes the Pannonian conflict, which begs the question what was Lentulus’s role that led him to attack the Dacians. If he was stationed in Macedonia or Thrace that would make perfect sense as a defensive action against raiding Dacian forces, but it seems unlikely that Rome would push across the Danube while they had rebellious Pannonians at their back. Therefore, it seems more likely that Lentulus’s campaign against the Dacians followed the defeat of the Pannonians or occurred immediately after their crossing of the Danube in 10 BC.
Based on the lack of detail about the campaign and its lack of long-term effect, it is likely that it was not particularly bloody and, as with Vinicius’s campaigns, was not intended as a campaign of conquest. Augustus decided to attack the Dacians because of the trouble they had caused and their potential for continuing trouble along the Danubian frontier in a region far from comfortably under Roman control or domination at this early stage. The intent therefore seems to have been to punish the Dacians for crossing the Danube in 10 BC and demonstrate to them, their allies and other hostile `barbarian’ peoples that such incursions would not be tolerated by Rome. It is likely that a second purpose of these campaigns was to push the Dacians and others further away from the Danube itself, creating a more secure frontier along the river by partially clearing the northern bank of potentially hostile peoples.
Lentulus’s and Vinicius’s campaigns against the Dacians, Bastarnae and Sarmatians are the ones referred to by Augustus in the Res Gestae where he informs his readers that under his auspices Roman armies crossed the Danube and compelled the Dacian people to submit to the will of Rome, a clear exaggeration of actual events. Clearly the actions of Augustus’s generals against the Dacians did not prevent future aggression, with a renewal of attacks towards the end of Augustus’s reign in AD 6, demonstrating that Augustus’s comments in the Res Gestae were at best an optimistic assessment of the effect Vinicius’s and Lentulus’s campaigns had had. At this point the Dacians had not yet re-instituted any form of the unification they had achieved under the leadership of Burebista and would again under Decebalus. Strabo indicates that at this time Dacia was split between four or five different tribes controlled by their own kings, making them much less of an overall threat. Like other tribal peoples that Rome had faced, it would have been difficult to put an end to the Dacian threat at this point because this would involve defeating all of the tribes simultaneously in order not to allow one defeated tribe to rebuild its strength while Roman forces were engaged against another, a situation seen in Germany.