Agricola, advancing through Scotland almost to present Aberdeen in 83 or, less probably, 84, with eleven thousand Roman cavalry and infantry comprising Romans and loyal Britons, meets and fights thirty thousand Caledones under Galgacus, or Calgacus, at Mons Graupius (an unidentified site in the Grampian Mountains in northeast Scotland).

Tacitus, our sole source for the event, avoids using terms such as king to describe Calgacus and it is uncertain as to whether the Caledonians had single leaders or whether they were more disparate and that Calgacus was an elected war leader only. (Tacitus only mentions him as giving a speech, probably fictitious).

Tacitus records the physical characteristics of the Caledonians as red hair and long limbs.

Although the Romans are outnumbered in their campaign against the tribes of Britain, they have often had difficulties in getting their foes to face them in open battle.

The Caledonians are the last to be subdued.

After many years of avoiding fight, the Caledonians are forced to join battle when the Romans march on the main granaries of the Caledonians, just as they had been filled from the harvest.

The Caledonians have no choice but to fight, or starve over the next winter.

It is said that the Roman Legions took no part in the battle, being held in reserve throughout.

According to Tacitus, ten thousand Caledonian lives were lost at a cost of only three hundred and sixty auxiliary troops.

We must allow for the usual exaggeration of fatalities here however, as Roman accounts of enemy dead can be viewed as routinely suspect, especially with such a huge difference in numbers.

Twenty thousand Caledonians retreat into the woods, where they fare considerably better against pursuing forces.

Roman scouts are unable to locate the remaining Caledonian forces the next morning.

Following this final battle, it is proclaimed that Agricola has finally subdued all the tribes of Britain, which is not strictly true, as the Caledonians and their allies remain a threat.

Indeed, even if the inflated account of Caledonian fatalities were to be accepted, the bulk of their forces are still intact to fight again.

Soon after Agricola is recalled to Rome, and his post passes to Sallustius Lucullus.

It is likely that Rome intended to continue the conflict but that military requirements elsewhere in the empire necessitated a troop withdrawal and the opportunity was lost.

Tacitus' statement Perdomita Britannia et statim missa (Britain was completely conquered and immediately let go), denotes his bitter disapproval of Domitian's failure to unify the whole island under Roman rule after Agricola's successful campaign.

There are no other accounts of the battle apart from Tacitus's account, though this is not unusual given the scanty nature of sources in general for this period of history.

We have no legends or traditions whatsoever from the native inhabitants of Caledonia.

While Agricola was Tacitus's father in law and therefore is undeniably biased towards the subject of his history, he is generally regarded as one of the most reliable historians of the period.