In 16 BC, after the celebration of the Secular Games, Augustus left Rome for Gaul. This replicated his behaviour after 27 BC when he had also left to engage in a programme of provincial conquest. Malicious gossip suggested that he left so as to continue his affair with Terentia, wife of Maecenas, to avoid the unpopularity that his reforms had brought upon him, and to pursue a programme of conquest (Dio, 54.19).
The Augustan period saw a sustained programme of conquest in the West.
In 27 BC, Augustus had headed to Gaul, seemingly with the intention of invading Britain. The invasion was delayed. The crossing made the logistics difficult and meant that considerable preparation was needed. But it remained a plan. He looked to resolve problems in Gaul and Spain and after holding a census in Gaul, he went to Spain (Dio, 53.22).
In 26, he was again in Gaul planning for the invasion of Britain. But again he was distracted. The Salassi an Alpine tribe in the Val d’Aosta revolted. The Salassi had been supposedly defeated conclusively in 35 BC by Valerius Messalla (Dio, 49.38). Yet it is is something of a theme of the accounts of the conquest of the West that defeated tribes are suppressed on multiple occasions. At the same time, war broke out in Spain and Augustus personally led armies against the Cantabri and Astures (Dio, 53.25-26) (map).
Both wars were successful and colonies were planted at Augusta Praetoria (Aosta) and Augusta Emerita (Merida), now a world heritage site. The colonies served both to secure the newly conquered territory by establishing a permanent Roman force in the region and to reward and settle the veterans.
If that stage of the war in the Alps was settled relatively quickly, the war in Spain dragged on. Augustus claimed to have brought the war to an end, but the Cantabri (map) and Astures were not conclusively defeated.
There was also war in Germany about which we have almost no details (Dio, 53.26).
The war in Spain ‘resumed’ in 24. The governor responded by devastating the tribal lands and chopping the hands off anyone they caught (Dio, 53.29). Not even this quelled resistance. The war continued into 22 BC when a Roman campaign led to mass suicides among the Cantabri and the supposed subjugation of the Astures (Dio, 54.5).
Augustus headed East in 21 BC and Agrippa was sent to Rome. He was soon needed elsewhere and he campaigned in Germany before returning once more to the rebellious Cantabri. Dio sees the resumption of violence as resulting from Cantabrian slaves killing their masters and escaping to continue the resistance. It is surely more likely that the war never stopped. Now, Agrippa took charge. He found the legions mutinous after so long and so unsuccessful a campaign. Legions lost honours and discipline was restored. The Cantabri were once more assaulted and Agrippa appears to have killed many of those of military age and forcibly relocated many others. The result was another declaration of another Roman victory (Dio, 54.11).
In 16 BC, the focus of Roman campaigning shifted, though there is further references to war in Spain. Augustus went to Gaul to deal with war on multiple fronts. Three German tribes had massacred Romans settled amongst them and crossed the Rhine into Gaul. They defeated an army under Marcus Lollius, perhaps leading to the loss of a legion (Velleius Paterculus, 2.89) . The Alpine region was also at war with two tribes being suppressed by a Publius Silius. To the east, Istria (an area of Croatia) was invaded by the Norici and Pannonians.
This invasion of Istria brought barbarians into what was probably Italian territory. They were driven off by Silius. The Danube also proved a troublesome area, with campaigns against the Bessi, and the Dentheleti and the Scordisci in Macedonia (Dio, 54.20).
The next stage of the expansion as probably in the following year. This time, members of the imperial family, Tiberius and Drusus, were at the forefront of the campaigning, the target being the region the became known as Raetia.
The war was supposedly sparked by Raetian atrocities and raids into Italy and Gaul. Drusus crossed from the region of Padua-Verona, fighting his way through the mountains. Tiberius also invaded, perhaps from further to the west. Mass deportation followed the military success (Dio, 54.22).
In 14 BC, the military expansionism continued without obvious break. The Ligurian Alps were attacked, though the region had been under some level of Roman control for some time.
The war against the Pannonians was continued, pushing Roman power northwards from Illyricum towards the Danube. Agrippa was sent to exert Roman authority north of the Black Sea (Dio, 54.24).
In 13 BC, Augustus returned to Rome. He had been on campaign for three years. Tiberius was consul. Drusus continued to campaign in Germany. Agrippa campaigned in Pannonia. He died in 12 BC (Dio, 54.28). The wars simply continued. Tiberius fought against the Pannonians and Dalmatia. Drusus raided into Germany, establishing a seemingly more permanent Roman presence on the eastern bank of the Rhine, campaigns that stretched into 10 BC (Dio, 54.33-36).
Drusus was himself consul in 9 BC. He seems to have spent very little time in Rome, but resumed his conquests in Germany. He reached as far as the Elbe and set up trophies to commemorate his victories. Germany between the Elbe and the Rhine was under considerable Roman pressure. Tiberius meanwhile pressed towards the Danube (Dio, 55.1).
With the death of Drusus, Tiberius was transferred to the German frontier and campaigned extensively across the Rhine. But after this point, campaigning in Germany slowed. It seems as if the Romans entered a consolidation phase. Tiberius returned to Rome and then spectacularly retired from politics. Augustus himself was now old and not in a state to lead the troops himself. Also, our main source, Dio, becomes fragmentary at this stage.
There were still campaigns. Domitius managed to cross the Elbe, something Drusus had not achieved (Dio, 55.10a) and the recall of Tiberius in AD 4 led to a resumption of expansionist wars. This all came to an end with the Pannonian revolt (Dio, 55.28)
If you put these years on a map, a consistent pattern stands out. The Republic had seen an unsystematic Roman expansion in the West. The Mediterranean littorals had fallen under Roman control during the third and second centuries BC. Spain was beset by long drawn-out campaigns into the centre of the peninsula. Away from the coastal regions, Roman power had limited itself to Macedonia. With Julius Caesar Roman power had lurched northwards, capturing Gaul.
Augustus expansion looks systematic. But the system might be illusory. Rome advanced on all frontiers in the West often simultaneously. The initial desire to go to Britain was probably shaped by a wish to emulate Julius Caesar, but when that proved impossible, attention shifted elsewhere.
The conquest of Spain was completed. There were numerous declarations of the successful end of the war, but it really does seem to have brought to a victorious conclusion by Agrippa. This thereby ended the process of Roman conquest that had been on-going for more than 150 years.
That gives us a clue to the Roman processes of conquest. It was not done in a single campaign that took control over the key places and imposed a government. In the West, it came through repeated and vert violent raids that might take place over decades and which must have gradually degraded the capacities of the population to resist. Then, eventually, the Romans moved in and stayed.
The Alpine region, difficult to conquer, was subjected to a series of campaigns that might have stretched over 20 years: the massive victory monument of the Tropaeum Alpium at La Turbie seems to declare an end to the war in 7 BC. Pliny the Elder gives us a list of the tribes captured in his Natural History 3. 136-37. The various tribal names are in bold below:
IMP · CAESARI DIVI FILIO AVG · PONT · MAX · IMP · XIIII · TR · POT · XVII · S · P · Q · R · QVOD EIVS DVCTV AVSPICIISQVE GENTES ALPINAE OMNES QVAE A MARI SVPERO AD INFERVM PERTINEBANT SVB IMPERIVM P · R · SVNT REDACTAE · GENTES ALPINAE DEVICTAE TRVMPILINI · CAMVNNI · VENOSTES // VENNONETES · ISARCI · BREVNI · GENAVNES · FOCVNATES · VINDELICORVM GENTES QVATTVOR · COSVANETES · RVCINATES · LICATES · CATENATES · AMBISONTES · RVGVSCI · SVANETES · CALVCONES · BRIXENETES · LEPONTI · VBERI · NANTVATES · SEDVNI · VARAGRI · SALASSI · ACITAVONES · MEDVLLI · VCENNI · CATVRIGES · BRIGIANI · SOGIONTI · BRODIONTI · NEMALONI · EDENATES · VESVBIANI · VEAMINI · GALLITAE · TRIVLLATI · ECDINI · VERGVNNI · EGVI · TVRI · NEMATVRI · ORATELLI · NERVSI · VELAVNI · SVETRI.
The Alpine wars were clearly more extensive and long-lasting than our sources register and this reflects a fundamental problem in understanding military expansion in the West in particular. In the imperial period we tend only to hear about wars which for some reason or another had an effect on Roman politics: because the emperors or their families were involved or because the war had larger political consequences. Small wars and localised campaigns likely never get reported to us and we have to assume that in periods of conquest, there were many campaigns which have left no trace on our historical record.
The drive through Raetia brought the land north of the Alps into Roman control. Roman forces pushed across the Balkans, extending their power towards the Danube. In Germany, they consolidated control at the Rhine frontier and then advanced as far as the Elbe.
Historically, the Romans came to portray Germany as unconquerable. But that is to ignore the fact that before the revolt of AD 9, Germany seemed to be conquered. A decade later, Germanicus’ ambition to conquer Germany was dismissed by Tiberius, but there is every reason to think it was realistic.
Dio finds enemies to blame for each stage of the expansion. Rome was provoked. Presumably there were some very stupid tribes out there who failed to see the risks.
But if an imperial power is repeatedly and systematically provoked into invasions, it starts to look as though they might be being very aggressive. Examined over the nearly three decades of continuous expansion on multiple fronts, it is abundantly clear that the Romans were expanding methodically and crushing all resistance in their path.