Agricola, a shrewd and enlightened ruler who has gradually Romanized Britain, encouraging urbanization and fostering partial self-rule in the south, is recalled in 85, after an unusually long tenure as governor.

Tacitus claims that Domitian ordered his recall because Agricola's successes outshone the Emperor's own modest victories in Germany.

The relationship between Agricola and the Emperor is unclear: on the one hand, Agricola is awarded triumphal decorations and a statue (the highest military honors apart from an actual triumph); on the other, Agricola will never again hold a civil or military post, in spite of his experience and renown.

He is offered the governorship of the province of Africa, but declines it, whether due to ill health or (as Tacitus claims) the machinations of Domitian.

There appears to have been a serious setback at the hands of the tribes of the Picts of Alba around 105 CE: several Roman forts are destroyed by fire, with human remains and damaged armor at Trimontium (at modern Newstead, in southeast Scotland) indicating hostilities at least at this site.

There is also circumstantial evidence that auxiliary reinforcements were sent from Germany, and an unnamed British war of the period is mentioned on the gravestone of a tribune of Cyrene.

However, Trajan's Dacian Wars may have led to troop reductions in the area or even total withdrawal followed by slighting of the forts by the Picts rather than an unrecorded military defeat.

The Romans are also in the habit of destroying their own forts during an orderly withdrawal, in order to deny resources to an enemy.

In either case, …

A large force of Sarmatian cavalry, consisting of five thousand five hundred Iazygean men, arrives in Britannia in 175, probably to reinforce troops fighting unrecorded uprisings.

The large fort at Newstead is maintained along with seven smaller outposts until at least 180, when the Romans, in the face of Caledonian pressure, abandon the Antonine Wall, making a permanent withdrawal to Hadrian’s Wall.

Ulpius Marcellus is recorded as governor of Roman Britain in an inscription of 176-80, and apparently returns to Rome after a tenure without serious incident.

He is sent out again by the Emperor Commodus to suppress a serious revolt in 180, which earns him the reputation of a disciplinariian.

Dio Cassius records that tribes from the north breached Hadrian's Wall, which separated them from the empire, and killed a general (possibly Marcellus' predecessor, Caerellius Priscus) with all his guards, presumably during an inspection of Hadrian's Wall.

Little else is known of the revolt except that Dio called it the most serious war of Commodus' reign.

Severus travels to Britain in 208 with the intention of conquering Caledonia.

Modern archaeological discoveries have made the scope and direction of his northern campaign better understood.

Severus likely arrives in Britain possessing an army over forty thousand, considering some of the camps constructed during his campaign could house this number.

He strengthens Hadrian's Wall and reconquers the Southern Uplands up to the Antonine Wall, which is also enhanced.

Severus builds a one hundred and sixty-five-acre camp south of the Antonine Wall at Trimontium, likely assembling his forces there.

Severus then thrusts north with his army across the wall into enemy territory.