Caligula’s Planned Invasion of Britain

Caligula: An Unexpected General

By Lee Fratantuono

Gaius Caligula reigned for four short years from 37 to 41 CE before his infamous tenure came to a violent end. While much has been written about Caligulas notorious excesses and court life, relatively little of his military and foreign policy has been seriously studied.This is a military history of Rome during Caligulas reign. Caligula had been raised in a military camp (his nickname, Caligula, means Little Boot. His years as emperor came in the wake of the great consolidation of Tiberius gains in Germany and Pannonia, and in large part made possible the invasions of Gaul and Britain that were undertaken by his uncle and successor, Claudius. His expeditions in Gaul were part of a program of imitation of his storied predecessor, and crowning completion of what had been left undone in the relatively conservative military policy years of Augustus and Tiberius.Caligula: An Unexpected General offers a new appraisal of Caligula as a surprisingly competent military strategist, arguing that his achievements helped to secure Roman military power in Europe for a generation.

Caligula may have planned a campaign against the Britons in AD 40, but its execution was unclear: according to Suetonius’ The Twelve Caesars, he drew up his troops in battle formation facing the English Channel and, once his forces had become quite confused, ordered them to gather seashells, referring to them as “plunder from the ocean due to the Capitol and the Palace”. Alternatively, he may have actually told them to gather “huts”, since the word musculi was also soldier’s slang for engineers’ huts and Caligula himself was very familiar with the Empire’s soldiers. In any case this readied the troops and facilities that would make Claudius’ invasion possible three years later. For example, Caligula built a lighthouse at Bononia (modern Boulogne-sur-Mer), the Tour D’Ordre, that provided a model for the one built soon after at Dubris (Dover).

Consuls, army commanders, even members of the Emperor’s own family – all had joined in the conspiracy against him, and still their plotting had failed. Nevertheless, the shock to Caligula’s self-assurance had been seismic, and his bitterness towards his sisters unsurprising. Though he had moved swiftly and ruthlessly to crush rebellion along the Rhine and to stabilise Rome’s most militarily significant frontier, he had been left with little choice but to spend the winter reining in his plans for the conquest of Germany. The risk of further treachery was simply too great. The scale of Caligula’s suspicions was laid bare when the Senate, frantic to cover its own back, sent a delegation of grandees led by Claudius to congratulate him on his foiling of Lepidus’s conspiracy. The Emperor treated the embassy with open contempt. Most of the senators were refused entry to Gaul as potential spies; Claudius, when he arrived in Lugdunum at the head of the few granted access to the city, was pushed fully clothed into the river. Or so the story went. True or not, the rumour rammed home the point that Caligula wished to make. Those who had betrayed him could no longer expect to receive any marks of courtesy or respect. Both the Senate and his own family had been marked down as a nest of vipers. The state of war between emperor and aristocracy was now official.

All of which made it essential for Caligula to return to Italy as soon as possible. Nevertheless, this presented him with a challenge. It was clearly out of the question to depart the North without some feat to his name that he could promote in Rome as a ringing victory. So it was, with the first approach of spring, that he returned to the German front, where he inspected troops, noted with approval the improvements made by Galba to standards of discipline, and ventured another sally across the Rhine. In the event, though, it was not Germany which was to provide Caligula with the coup he so desperately needed, but Britain.

There, despite the fact that no legions had crossed the Channel in almost a century, Roman influence had been steadily growing. With the island carved up between an assortment of fractious and ambitious chieftains, it was only to be expected that Rome should provide them with the readiest model of power. The most effective way for a British warlord to throw his weight around was to ape the look of Caesar. The king who entertained his guests with delicacies imported from the Mediterranean, or portrayed himself on silver coins sporting a laurel wreath, was branding himself a man on the make. Such displays of self-promotion did not come cheap or easy – and it was no coincidence that the most powerful of the island’s chieftains had always made a point of staying on the right side of Rome. Cunobelin was the king of a people named the Catuvellauni, whose sway extended over much of eastern and central Britain; but that had not prevented him from setting up offerings on the Capitol, and from being assiduous in returning any Roman seafarers shipwrecked off his kingdom. Unsurprisingly, then, when one of Cunobelin’s sons was exiled after launching an abortive land-grab on Kent, the presence of Caesar on the opposite side of the Channel ensured that there was only one place for him to head.

Caligula, naturally, was delighted by this unexpected windfall. The arrival of a genuine British prince could hardly have been more timely. It was a simple matter, receiving the surrender of such a man, to represent it as the surrender of the whole of Britain. Couriers were promptly dispatched to Rome. They were ordered, on their arrival in the city, to ride as ostentatiously through the streets as possible, to proceed to the temple of Mars, and there to hand over the Emperor’s laurel-wreathed letter to the consuls. The Roman people had their tidings of victory.

And sure enough, borne on the surging of rumour, the news of it was duly repeated through the city: the dangers braved by Caesar, the captives he had taken, the conquest he had made of the Ocean. These were the kinds of detail that his fellow citizens had always loved to hear. Yet even as they were being repeated across Rome, from the Forum to taverns and washing-hung courtyards, other accounts of Caesar’s doings in the North were also circulating: cross-tides of gossip altogether less flattering to Caligula. It was claimed that he had scarpered back across the Rhine at the merest mention of barbarians; that the spoils of his supposed conquest of the Ocean were nothing but chests filled with shells; that the captives he was bringing back with him to Rome were not Germans at all, but Gauls with dyed hair. Caesonia, ever her husband’s partner in bombast and theatricality, was even claimed to be sourcing ‘auburn wigs’ for them to wear. How was anyone in Rome, far removed from the front, to judge between two such different slipstreams of propaganda? Caligula himself, returning at high speed from the Channel for Italy, had no doubt what was at stake – nor whom to blame for the blackening of his war record. ‘Yes, I am heading back – but only because the equestrians and the people want me back,’ he informed a delegation of senators who had travelled north to meet him. ‘Do not think me a fellow citizen of yours, though. As Princeps, I no longer acknowledge the Senate.’