Roman sources tell of larger campaigns east of the Rhine and north of the Danube during the third century, especially for the reigns of emperors Caracalla (in the year 213) and Maximinus Thrax (in the year 235).
While this has been known to historians for a long time, there was never any archaeological proof of any campaign during this time within the Germania Magna.
The sources are unclear on the extent of such military operations.
It was assumed that they took place near the Limes.
The few sources that suggested otherwise were assumed to be unreliable.
The Battle at the Harzhorn, as interpreted by the artifacts found to date, now proves that the Romans went far deeper into Germania during the third century than was thought possible earlier.
There is no explicit date for the battle.
A coin minted under and showing the portrait of emperor Commodus and some specific pieces of military equipment originally dated the battle to after 180.
A hypothesis suggested the early third century, such as the supposed Germanic campaigns of emperors Caracalla and Maximinus Thrax.
Both of these are attested in historical sources, but no archaeological proof had been found so far.
Later coinage finds depicting emperors Elagabal (218-222) and Severus Alexander (222-235) further suggests Maximinus Thrax's campaigns.
The Historia Augusta, a late Roman collection of biographies of the Roman Emperors, mentions that Maximinus Thrax marched north from Moguntiacum (today's Mainz) about three hundred (trecenta) to four hundred (quadringenta) Roman miles.
Since this was thought to be impossible, this passage was often changed to triginta and quadraginta (thirty to forty miles).
Numismatic Frank Berger dates the battle to between 230 and 235.
Germanic tribes had crossed the Rhine and devastated the Roman countryside in 233, in 235, Maximinus Thrax leads the revenge campaign into Germania, which had been prepared by his predecessor Severus Alexander.
