We are extremely fortunate in the case of this man in that his son-in-law was none other than Gaius Cornelius Tacitus, the prolific Roman writer and historian, who recorded in The Agricola the biography of this great man, which remains the only surviving biography of a Roman general outside of the imperial families. This document records the campaigns not only of Agricola himself, but of all the men who preceeded him in the post of pro-praetorian governor of Britain, albeit in an abbreviated form.
The conquests of this general were to see the Roman province of Britannia at its greatest extent; his seven campaign seasons in Britain can be summarized as follows:
Anyone who has cultivated an interest in Roman Britain must admire the vitality and military genius of Gnaeus Julius Agricola, the Roman governor of Britain who, in just seven short years, advanced the military occupation of the islands from his initial campaigns against the Ordovices tribe of North Wales, through the territories of the powerful Brigantes tribe of northern England, and the tribes of lowland Scotland and the eastern Highlands, possibly as far north as Inverness on the Moray Firth. In his seven years as military governor of Britain, Agricola more than doubled the area of the province which, up until then, had taken his ten predecessors a period of thirty-five years to conquer and control. His campaigns in Scotland culminated in the decisive defeat of the combined Caledonian army under the war-lord Calgacus in a pitched battle at Mons Graupius. The actual site of this battle has provoked much discussion in modern academic circles, but was perhaps at Durno in Aberdeenshire/Grampian. Such was Agricola's generalship in this encounter that the citizen soldiers of the legionary forces at his disposal were not even employed in the fighting, the battle being won by tactical use of his peregrine auxiliary regiments. This victory made him, perhaps, even more popular at Rome than the emperor Domitian himself, who, seeing his popularity being eclipsed by a mere lieutenant, immediately ordered Agricola's withdrawal from Britain, to be "fobbed-off" with triumphal regalia and an early-retirement.
The campaigns of this eminentissimus vir took him from North Wales through northern England almost to the northern tip of Scotland, along the way passing through some of the most spectacular scenery that Britain has to offer, from the marching camp at Pen-y-Gwrhyd at the foot of Mount Snowdon and the druidic stronghold on the Isle of Anglesey, to the ancient cities of Chester, Lincoln and York all of which saw legionary activity under Agricola. He left forts guarding his supply-routes across the Pennines into northern England, and there are many Agricolan foundations along the Stanegate, the precursor of Hadrian's Wall, particularly impressive remains may be seen at Chesterholm/Vindolanda and the legionary storage compound at Corbridge, with less-impressive remains at Carvoran, but most of his foundations are now nothing but crop-marks in fields, or perhaps still waiting to be found or confirmed, like the possible site of Portus Trucculensis at Kirkbride on the Cumbrian coast. In Scotland, Agricola's campaigns took him from Glenluce near the Rhinns of Galloway in the south-west, within sight of Northern Ireland across the Irish Sea, through the strategic site of Newstead/Trimontium beneath the Eildon Hills in the Scottish Borders Region, to his fortifications along the Forth and Clyde estuaries, many of which were so well placed that they were later encorporated within the line of the Antonine Wall. The Agricolan campaigns through Central, Tayside and Grampian in eastern Scotland have left behind an archaeological legacy in the form of many temporary marching camps, although many of these original encampment sites were re-used and confused by later campaigns.
| Name | N.G.Ref. | Description |
|---|---|---|
| DEVA (Chester) | SJ4066 | legionary fortress Legio XX Valeria. |
| VIROCONIVM (Wroxeter, Shropshire) | SJ5608 | reduced strength fortress Vex Legio XX Valeria. |
| ISCA SILVRVM (Caerleon, Gwent) | ST3390 | legionary fortress Legio II Augusta. |
| LEVOBRINTA (Forden Gaer, Powys) | SO2098 | fort |
| Caersws, Powys | SO0292 | fort |
| Trawsgoed, Dyfed | SN6772 | fort |
| Castell Collen, Powys | SO0562 | fort |
| CICVCIVM (Brecon Gaer, Y Gaer, Powys) | SO0029 | fort |
| Coelbren, West Glamorgan | SN8510 | fort |
| NIDVM (Neath, West Glamorgan) | SS7497 | fort |
| Cardiff, South Glamorgan | ST1876 | fort |
| BVRRIVM (Usk, Gwent) | SO3700 | fort |
| Caerphilly, Mid Glamorgan | ST1688 | fort |
| Gelligaer, Mid Glamorgan | ST1397 | fort |
| Pen-y-Darren, Mid Glamorgan | SO0506 | fort |
| Caergai, Gwynedd | SH8731 | fort |
| Tomen-y-Mur, Gwynedd | SH7038 | fort |
| Bryn-y-Gefeiliau, Gwynedd | SH7457 | fort |
| CANOVIVM (Caerhun, Gwynedd) | SH7770 | fort |
| Pen Llystyn, Gwynedd | SH4844 | fort |
| SEGONTIVM (Caernarfon, Gwynedd) | SH4862 | fort |
| Name | N.G.Ref. | Description |
|---|---|---|
| EBVRACVM (York) | SE6052 | legionary fortress Legio IX Hispana. |
| LINDVM (Lincoln) | SK9771 | legionary fortress Legio II Adiutrix. |
| PETVARIA (Brough-on-Humber) | SE9326 | fort |
| DERVENTIO (Malton) | SE7971 | large fort |
| CORSTOPITVM (Corbridge) | NY9864 | fort and storage depot |
Notably, no permanent Agricolan fortifications have been identified in the Lake District, which may point to Agricola (or one of his immediate predecessors) having obtained a treaty with the Carvetii tribe of Cumbria. 
| Name | N.G.Ref. | Description |
|---|---|---|
| TRIMONTIVM (Newstead, Borders) | NT5734 | large fort in the Tweed Valley |
| Milton (Dumfries & Galloway) | NT0901 | large fort in Annandale |
| CAMELON (Camelon, Central) | NS8680 | large fort on the Forth |
| Dalswinton (Dumfries & Galloway) | NX9384 | large fort in Nithsdale |
| Castledykes (Strathclyde) | NS9244 | large fort in Clydesdale |
| Glenlochar (Dumfries & Galloway) | NX7364 | large fort |
| Oakwood (Borders) | NT4224 | fort |
| Easter Happrew (Borders) | NT1940 | fort |
| Barochan (Strathclyde) | NS4169 | fort |
| BLATOBVLGIVM (Birrens, Dumfries & Galloway) | NY2175 | fort |
| Mollins (Strathclyde) | NS7171 | small fort |
| Gatehouse of Fleet (Dumfries & Galloway) | NX5957 | fortlet |
| Glenluce (Dumfries & Galloway) | NX1956 | Marching Camp |
| Evidence \ Site | Castlecary | Cadder | Mumrills | Balmuildy | Kirkintilloch | Old Kilpatrick |
|---|---|---|---|---|---|---|
| 1st-century glass | X | X | ||||
| 1st-century samian-ware | X | X | ||||
| 1st-century bronze coins | X | X | X | X | ||
| 'pre-Hadrianic' pottery | X | X | X | X |
The evidence tabulated above would certainly seem to support an Agricolan foundation for Castlecary, probably also for Mumrills, Cadder and Balmuildy, and though the sparse evidence at the other two sites may testify Agricolan occupation, any such claims should be treated with caution.
Two fortlets discovered from the air at Croy Hill and Bar Hill appeared to lie beneath the Antonine forts and were thought on this basis to be Agricolan. Subsequent fieldwork at each of these sites have since confirmed that both fortlets actually post-date the Antonine Wall forts, and have thus been assigned to the re-occupation of this northernmost frontier during the early AD160's.
It is possible, indeed probable, that Agricola built no permanent forts north of the Forth/Clyde isthmus. However, there is evidence of two phases of first-century occupation in two forts along the Roman road into Tayside at Ardoch and Strageath. The former fort may have been founded during Agricola's third campaign season and the latter during the sixth, though it is equally likely that each was built by Agricola's successor Sallustius Lucullus.
Prompted by jealousy, the emperor Domitian recalled Agricola in ad84 and granted him triumphal regalia, after which he was quietly retired. Before long, perhaps as early as 87, Legio II Adiutrix were withdrawn from Britain and the new fortress of Legio XX Valeria Victrix at Inchtuthill had to be abandoned before its completion, the Twentieth being withdrawn from the Scottish Highlands to reoccupy the recently vacated fortress of the Second Adiutrix at Chester. In the space of a few short years much of Agricola's gains in Scotland were gradually abandoned as many auxiliary units were withdrawn from Britain to fuel wars on the Continent with the remainder of the Scottish garrison being positioned along the line of the Stanegate in northern England and a few outlying forts along the main access-routes into the lowlands.

Despite the massive military operations conducted by Agricola in Britain there is little in the way of epigraphic evidence to show for all his efforts. This is primarily because most of his time as governor was spent on active campaign, with almost the entire British army living in field conditions, and the temporary nature of these "marching" encampments tends to rule out any permanent epigraphic record in the way of inscribed building or altar-stones, which are prevalent in the permanent fortifications. Indeed, the only records of Agricola's governorship are pieces of lead piping inscribed with his name from the timber-built fortress of the Second Adiutrix at Chester, and a fragmentary inscription from Verulamium/Saint Alban's in Hertfordshire, which was a long way away from any of the fighting. Not much to show for the longest known tenure of service for any propraetor assigned to Britain