Augustus formulated a policy for an empire which had evolved haphazardly over the previous centuries. The empire should not expand further, but its frontiers should be made more secure. Only two emperors seriously violated this principle: Claudius with his invasion of Britain, and Trajan with his conquest of Dacia.


In republican times, the empire had been allowed to expand as opportunity, circumstances, and the senate decreed. Augustus recognized the need for a specific foreign policy and saw that to undertake random wars of aggression in pursuit of new conquests was an uneconomic way of exercising it. Military success, however, was a Roman way of life, but he would ensure that it was gained by consolidating provinces and their defences, without enabling any commander to aspire to an overwhelming personal following among his troops. The frontiers of the empire developed according to the lines to which he had withdrawn following the disaster in AD 9, when Publius Quintilius Varus lost three complete legions, three cavalry regiments, and six auxiliary cohorts, after being enticed into unfamiliar territory between the rivers Weser and Ems.

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The extent of the Roman empire during the rule of Hadrian, including places and peoples outside Italy mentioned on this site. Copyright © Taylor & Francis Group

Tiberius was advised by Augustus not to try to extend the boundaries of the empire. His immediate successors were either too suspicious or too frightened of the army to do much else, with the exception of Claudius and his invasion of Britain in 43 AD. He also altered the status of Mauretania and Thrace from client kingdoms to provinces.


Scene from Trajan’s column: the river god Danubius watches legionaries crossing a pontoon bridge. (VRoma: AICT)

In AD 101 Trajan crossed the river Danube into Dacia, without waiting to give a chance to the treaty agreed between Domitian and the king of Dacia. This resulted in a great victory but dubious long-term advantage, and Dacia was finally evacuated of Roman troops in AD 275.

Some legions remained on the same station for many years; others were deployed as the situation demanded. The Second Augusta and the Twentieth Valeria Victrix spearheaded the invasion of Britain in AD 43 and were among the last to be evacuated in AD 400. The Twentieth was also Agricola’s strike force in northern Britain, and helped to build both Hadrian’s and the Antonine walls.


Plaster cast of distance-slab from the Antonine Wall. (VRoma: Hunterian Museum, Glasgow: Susan Bonvallet)

Originally, the extent of occupation of a region was bounded by a limes (plural limites), which just meant a path or track. Then it came to refer to a military road which linked the permanent forts housing units of a legion, whose task it was to discourage hostile military gatherings beyond the line, keep the peace and encourage Romanization within it, and allow free movement for trade across it. Thus limes came to mean boundary or frontier and the English word from it to signify something which “may not be passed”. Sometimes, as in the cases of Hadrian’s and the Antonine walls in Britain, the limes was an actual wall.

Hadrian also reviewed the physical boundaries of the whole empire, and strengthened with a wooden palisade the defences of the Rhine.


Reconstructed fortification marking the boundary of the Roman empire in Germany, showing palisade and ditch. (VRoma: Saalburg Museum: Barbara McManus)


Distance slab

The inscription, when expanded, reads in translation: “For the Emperor Caesar Titus Aelius Hadrianus Antoninus Augustus Pius, Father of His Country, a detachment of the Twentieth Valerian and Victorious legion completed [this part of the wall] over a distance of 3000 feet.”


Although Dacia was only a province of Rome for less than two centuries, the short spell of Romanization had a lasting effect, both on the language of the territory and its modern name - Romania.

This is the final page of the section on the Roman army. You can review the illustrations used (many at a larger size) in Gallery 8.

Believe it or not:

One of the most advanced legionary fortresses, at Inchtuthil, in Perthshire, Scotland, was never used at all! Probably intended as the headquarters of the Twentieth Legion, and begun in the autumn of AD 84, it was to incorporate 66 barrack blocks, stores, workshops, administrative offices, eight granaries, separate houses for the commanding officer and senior officers, and a hospital with 60 five-bedded wards. It was abandoned half-way through the building process, and everything that could not be removed was destroyed. Drains and sewers were filled with gravel or with finely pounded fragments of earthenware and glass. The complete contents of a pottery store was systematically smashed to pieces. A workshop’s stock of 750,000 unused, hand-forged nails, between 5 cm and 40 cm long, was poured into a pit 4 m deep, and covered with a layer of soil 2 m thick, which was then packed down. When the nails were uncovered almost 1900 years later, because of the action of the oxygen in the groundwater, the inner core of nails were virtually new, with clean-cut heads and edges, and bright patches of metal shining through a negligible coating of rust.