Caligula & the 2nd Invasion of Britain (40AD)

Emperor Gaius Caesar Augustus Germanicus, popularly known – amongst the legions – as Caligula (after the ‘little military boots’ that he had worn as a child) is thought to have staged a mock invasion of Britain.

The sources for this story are Suetonius, Cassius Dio and Aurelius Victor none of them contemporaries of Caligula, and possibly relying upon sources hostile to him. A summary of the story is after wintering in Gaul and engaged in some allegedly farcical operations on the German frontier, Caligula drew up his forces with their equipment on the shores of the Ocean. Briefly putting to sea, he returned to land and mounted a platform from which he ordered the signal for battle to be given. He then commanded the soldiers to gather sea-shells to be carried in his triumph in Rome. Finally, he ordered the construction of a lighthouse and promised the army a donative of one hundred denarii per man.

Below we will look at the source material for this and possible give some explanations.

Caligula Prepares to Campaign in the Rhineland

Early in his short reign (AD 39) Caligula left Rome to start a military campaign in Germany.

He had but one experience with military affairs or war, and then on a sudden impulse; for having gone to Mevania to visit the river Clitumnus and its grove, he was reminded of the necessity of recruiting his body-guard of Batavians and was seized with the idea of an expedition to Germany.

Suetonius, The Lives of the Caesars, The Life of Caligula, Chapter 43

In preparation for this Caligula prepared levies, which may have included the creation of two new legions, the X Primigenia and XX II Primigenia Legions from Mevania (modern Bevagna in northern Italy).

So without delay he assembled legions and auxiliaries from all quarters, holding levies everywhere with the utmost strictness, and collecting provisions of every kind on an unheard of scale.

Suetonius, The Lives of the Caesars, The Life of Caligula, Chapter 43

Caligula Travels to Germany

Caligula probably made for Mogontiacum (modern Mainz in Germany), a distance of about 700 miles (1100km). The Praetorian Guard marching on foot must have taken more than a month, although Caligula is said to have moved swiftly (for most of the journey).

Then he began his march and made it now so hurriedly and rapidly, that the praetorian cohorts were forced, contrary to all precedent, to lay their standards on the pack-animals and thus to follow him; again he was so lazy and luxurious that he was carried in a litter by eight bearers, requiring the inhabitants of the towns through which he passed to sweep the roads for him and sprinkle them to lay the dust.

Suetonius, The Lives of the Caesars, The Life of Caligula, Chapter 43

Mogontiacum lay at the heart of the Upper Rhine military district. The double fortress here was the springboard for campaigns across the river into the lands of the warlike Chatti. It seems to been occupied by the XIV Gemina and XVI Gallica legions. As soon as the XV Primigenia was raised, it probably was stationed nearby, and, if a campaign was soon to be undertaken reinforcements could be drawn from the other two legions further up the Rhine (the II Augusta and the XIII Gemina).

Gnaeus Cornelius Lentulus Gaetulicus is Executed

Ten years before, Caligula’s predecessor Tiberius had assigned the command of this powerful army to Gnaeus Cornelius Lentulus Gaetulicus, a position that he still held under Caligula. Lentulus sprang from an old patrician his agnomen Gaetulicus (‘conqueror of the Gaetulians’) commemorated his father’s successes against the Gaetulian tribe of North Africa in AD 6. A powerful and well-connected man like Lentulus might covet the position of emperor for himself – or so it might seem to a paranoid young man. At any rate, Lentulus was implicated in a major conspiracy and removed, to be replaced by Servius Sulpicius Galba.

In the first place, then, he put to death Lentulus Gaetulicus, who had an excellent reputation in every way and had been governor of Germany for ten years, for the reason that he was endeared to the soldiers.

Cassius Dio, Roman History Book 59 Chapter 22

Servius Sulpicius Galba Prepares for War

Having removed Lentulus, Caligula’s first priority was to install an effective replacement Servius Sulpicius Galba. As the newly appointed governor of Upper Germany he proceeded to toughen up the army of the province, rigorous exercises, which had apparently become slack under the lax command of his predecessor Gaetulicus. 

He got both the veterans and the new recruits into condition by plenty of hard work, speedily checked the barbarians, who had already made inroads even into Gaul, and when Gaius arrived,​ Galba and his army made such a good impression, that out of the great body of troops assembled from all the provinces none received greater commendation or richer rewards. 

Suetonius, The Lives of the Caesars, The Life of Galba, Chapter 6

Caligula arrives in Germany

By the time Caligula arrives in Germany with his troops there is not much for him to do and commentators ancient and modern have treated the idea of a serious campaign with derision.

soon, the enormous threats of Gaius Caesar were turned into farce.

Tacitus Germany 37.5

There does seem to have been an organised advance across the Rhine, but on finding that Germans had withdrawn, the troops returned. There were some ‘exercises’  in which Gaius ‘raided’ across the frontier, possibly in pursuit of his own troops, but nothing serious appears to have been attempted.

Presently, finding no one to fight with, he had a few Germans of his body-guard taken across the river and concealed there, and word brought him after luncheon with great bustle and confusion that the enemy were close at hand. Upon p475 this he rushed out with his friends and a part of the praetorian cavalry to the woods close by, and after cutting the branches from some trees and adorning them like trophies, he returned by torchlight, taunting those who had not followed him as timorous and cowardly, and presenting his companions and the partners in his victory with crowns of a new kind and of a new name, ornamented with figures of the sun, moon and stars, and called exploratoriae.​

Suetonius, The Lives of the Caesars, The Life of Caligula, Chapter 45

Taken alone, this passage could easily be construed as a description of some kind of military exercises. The only ambiguity concerns the “Germans in his bodyguard”, as Suetonius’ Latin could equally be rendered “Germans who were in custody”, but commentators have generally avoided this alternative
translation. After this passage, Suetonius continues:

Another time some hostages were taken from a common school and secretly sent on ahead of him, when he suddenly left a banquet and pursued them with the cavalry as if they were runaways, caught them, and brought them back in fetters, in this farce too showing immoderate extravagance. On coming back to the table, when some announced that the army was assembled, he urged them to take their places just as they were, in their coats of mail. He also admonished them in the familiar line of Vergil to “bear up and save themselves for better days.

Suetonius, The Lives of the Caesars, The Life of Caligula, Chapter 45

To the Romans, ‘hostages’ were representatives of allied or tributary nations, wiIIingly surrendered to the emperor as a pledge of loyalty and usually accommodated at Rome, where they could be educated in the Roman style.

It may be that Caligula had summoned some of those hostages from Rome, specifically those supplied by friendly German tribes. However, it seems more likely that this is another instance of Suetonius placing as
negative a slant as possible on one of Caligula’s actions. In fact, the story is remarkably similar to the previous one, except that the role of the hostages is there taken by “a few of the Germans in his bodyguard”. At any rate, the rest of the story could easily describe another of the Emperor’s military exercises, with troops taking their meal in full battle kit.

Briton named Adminius

After Caligula’s actions on the Rhine, Suetonius tells us that in AD39 a British prince named Adminius son of Cunobelin fell out with his father and fled to seek the emperors help. This was probably more correctly known as Amminus, the name that is found on silver coins of the period from southeast Britain. Suetonius tells us that Cunobelin controlled a substantial portion of south-eastern Britain, including the territories of the Catuvellauni and the Trinovantes.

All that he [Caligula] accomplished was to receive the surrender of Adminius, son of Cynobellinus king of the Britons, who had been banished by his father and had deserted to the Romans with a small force

Suetonius, The Lives of the Caesars, The Life of Caligula, Chapter 44

It is possible that Adminius’ arrival had encouraged Caligula to think of invading Britain, perhaps hoping to secure Cunobelinus’ throne for himself?

The Invasion of Britain

It is thought that Caligula marched his soldiers to the channel and ordered his soldiers to attack the waves and gather seashells as the spoils of victor.

Finally, as if he intended to bring the war to an end, he drew up a line of battle on the shore of the Ocean, arranging his ballista’s and other artillery; and when no one knew or could imagine what he was going to do, he suddenly bade them gather shells and fill their helmets and the folds of their gowns, calling them “spoils from the Ocean, due to the Capitol and Palatine.” As a monument of his victory he erected a lofty tower, from which lights were to shine at night to guide the course of ships, as from the Pharos.​ Then promising the soldiers a gratuity of a hundred denarii each, as if he had shown unprecedented liberality, he said, “Go your way happy; go your way rich.”

Suetonius, The Lives of the Caesars, The Life of Caligula, 46.

Cassius Dio’s Roman History relates the same story in slightly different terms, with specific mention
of Britain:

And when he reached the ocean, as if he were going to conduct a campaign in Britain, and had drawn up all the soldiers on the beach, he embarked on a trireme, and then, after putting out a little from the land, sailed back again. Next he took his seat on a lofty platform and gave the soldiers the signal as if for battle, bidding the trumpeters urge them on; then of a sudden he ordered them to gather up the shells. Having secured these spoils (for he needed booty, of course, for his triumphal procession), he became greatly elated, as if he had enslaved the very ocean; and he gave his soldiers many presents. The shells he took back to Rome for the purpose of exhibiting the booty to the people there as well.

Cassius Dio, Roman History Book 59 Chapter 25

The Christian theologian and historian Paulus Orosius gives a a similar account, although his work was probably derived from Suetonius. Orosius is best known for his work Historiarum Adversum Paganos (Seven Books of History Against the Pagans).  He briefly mentions Caligula, without referring to the order to collect sea-shells, adds nothing to our understanding of this incident.

Here, indeed, he set out with a great and incredible equipment to search for the enemy with idle forces, passing through Germany and France, and halted on the shore of the ocean about the prospect of Britain and having received Minocynobelinus, the son of the king of the Britons, who had been driven by his father with a few, into surrender, he returned to Rome in want of war material. 

Orosius, History Against the Pagans 7, 5, 5

Sextus Aurelius Victor (c. 320 – c. 390) was a historian and politician of the Roman Empire. Victor was the author of a short history of imperial Rome, entitled De Caesaribus and covering the period from Augustus to Constantius II. The work was published in 361.

Similarly he concentrated his legions in one place with the expectation of crossing over into Germany, then ordered them to gather mussels and cockles (conchas umbilicosque) on the shore of the Ocean while he himself went among them at times in the flowing robe of Venus, at other times, in full armour, he would say that he was taking the spoils not from men but from the gods, doubtless because he had heard that according to the Greeks, who love to embellish everything, fish of this kind are (called) Nymph’s eyes.

Aurelius Victor, De Caesaribus, 3, 11-12

Did Caligula try to Invade Britain?

There have been many interpretations of the writings of the historians. Was Caligula’s invasion plans were thwarted by a mutinous Legion and this task was used as as a way of humiliating them? There may be linguistic interpretation issues which have confused the issues or the historians may have just been writing anti Caligula propaganda.

It is commonly believed that Caligula declared war on Neptune, but this myth comes not from Suetonius but Robert Grave’s I, Claudius.