The Emperor Septimius Severus launched a campaign into Caledonia in 208AD and he used Trimontium as a camp during this new invasion. He made good progress at first, re-establishing some of the forts that Agricola had built and pushing into the Highlands. At this point, his army became bogged down as the Caledonian tribes used guerrilla warfare tactics. After Severus died in 211AD, his son and now Emperor Caracalla, withdrew again from Scotland and from Trimontium. One of the many beautiful finds at Trimontium was an intaglio bearing the profile of Caracalla, helping to date this period of occupation.
After this invasion the Romans never tried again although they did continue to send out scouts into Southern Scotland and trading links were also maintained with various tribes. Some people believe that a Roman province mentioned in Roman records, Valentia, may have been established in the 4th Century in Southern Scotland, but the exact location of this province is very unclear.
The Ravenna Cosmography utilises a 3rd- or 4th-century Roman map and identifies four loci (meeting places, possibly markets) in southern Scotland and which appear to have been meeting points for the Romans as well – it is possible that one of these may have been in or near to Trimontium.