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July/August

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When Rome invaded: Gerald Grainge considers the Channel crossing

Freedom Fighter - or Tale for Romans?
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ISSN 1357-4442

Editor Mike Pitts

features

The Romans are coming: but where?

We may know little about the details of the campaign, but the Roman invasion in AD43 was a turning point in British history. Gerald Grainge, archaeologist and experienced sailor, says the study of naval strategy can tell us much about the invasion crossing.

For much of the 20th century the academic consensus was that the Roman invasion of AD43, under Aulus Plautius, landed in east Kent. Two parallel defensive ditches found at Richborough on the Kent shore, dated to the invasion period, supported this proposition. However, there are problems in reconciling the idea of a Roman advance from east Kent to the Thames, and eventually to Colchester, with the main surviving documentary account, that of Dio Cassius's Roman History.

The first difficulty is the omen of a shooting star observed during the invasion crossing. Dio says that the legionaries were disheartened at being set back on their course, but took courage from a star shooting across the sky from east to west, "the direction in which they were sailing". However one interprets the incident, it is clear that Dio believed, and his readers would have understood him to mean, that the invasion fleet was sailing towards the west, a heading which cannot be reconciled with a course from Boulogne to east Kent.

The other problem is Dio's account of the submission of part of a tribe, which he names as the Bodunni, early in the campaign. The Bodunni are not otherwise known in contemporary sources, but it is thought Dio spoonerised the name of the Dobunni, known to be settled in Gloucestershire. His reference comes at an early stage in the campaign. Plautius, he says, gained by capitulation a part of the Bodunni, who were ruled by a tribe of the Catuvellauni; and leaving a garrison there, he advanced further and came to a river.

If the Romans landed in east Kent, this river must have been the Medway. It follows that the submission of a tribe living in Gloucestershire must have taken place before the invaders had left east Kent. While contemporary sources do occasionally report such remote capitulations, Dio's readers would have understood the reference to the garrison to imply that it was left in the territory of the Dobunni to protect them from the Catuvellauni. This could scarcely have happened, had not at least part of the Roman forces been active in the far west at this stage of the campaign. This is hardly compatible with the idea that the army landed in east Kent.

In 1989 JGF Hind proposed in the journal Britannia "an alternative strategy for Aulus Plautius". Hind's starting point was Dio's report that the new Emperor Claudius was persuaded to order the invasion by Verica, who had been expelled from Britain. Verica is known from his coins to have been king of the Atrebates, settled in southern Britain around Fishbourne Roman palace and the Roman town of Chichester. One of the campaign objectives would, therefore, have been to reinstall Verica. Hind suggested that the invasion fleet sailed, not for east Kent, but for the harbours of the Solent in the Atrebatic kingdom where it could expect a friendly reception. This idea was not only compatible with Dio's belief that the fleet was sailing westwards, but also provided a more credible context for the submission of the Dobunni and the establishment of a garrison in their territory. This, Hind suggested, could have been undertaken by "a flying column" detached from the main army while the latter consolidated its position in the Chichester area.

Although Hind accepted that his reinterpretation could not be proved, it has acquired something of the status of a new orthodoxy; certainly the hypothesis of a main landing at Richborough cannot now be advanced with the same level of confidence as before. However, I saw his concept of an invasion passage from Boulogne to the Solent, involving up to 1,000 ships, as a highly unseamanlike venture. I decided to investigate the naval strategy and logistics of the Channel crossing in the hope that this might offer clues as to the plausibility of a landing in the Solent.

In my investigation I considered what maritime archaeology can tell us of the ships the Romans might have used and their performance capabilities. I looked at the reality of a Channel crossing by an invasion fleet, considering not only the prevailing winds and the tidal regime, but also the special factors which apply to the management of fleets under sail. I also explored what we know of other invasion passages under sail, both to put the Claudian crossing in a strategic context, and to see what they might tell us of Roman naval practice.

Julius Caesar's accounts of his own expeditions to Britain in 55 and 54BC – when he embarked at Boulogne and landed in east Kent – make it clear that his invasion fleets comprised warships and transports. What he tells us, together with what we know from other documentary and iconographic sources, suggests that ancient oared warships were not suited for transporting legionaries and their bulky equipment. That was the function of the transports which made up the greater part of Caesar's fleets; it seems very likely that transports would have played the same role in the Claudian invasion.

We know a good deal about ancient Roman and Greek warships. They were armed with a ram, relied on oars for propulsion and their deep v-shaped lower hulls had a significant advantage in speed and manoeuvrability. In the invasion landing, equipped with catapults, slingsmen and archers, they would have brought covering fire to support the legionaries disembarking from the transports. Indeed, so formidable were they that Caesar tells us the Britons were "frightened by the shape of the ships, the motion of the oars, and the unfamiliar type of the artillery".

We know less about Roman transport ships, especially those used in north European waters. Even so, by a process of elimination, it can be concluded that the ships used as transports, both by Caesar and other Roman invaders of Britain, would have been built in the Romano-Celtic tradition seen in the excavated wrecks of St Peter Port 1 (Guernsey) or Blackfriars 1 (London). Such ships were robustly built with stout planking secured to massive framing timbers, with a single mast possibly rigged with a square sail. It is probable that these ships would have been very slow and unable to make effective progress to windward. They could not have sailed without a favourable wind.

For an invasion fleet made up of such ships the prospect of sailing westwards from Boulogne to the Solent would have been much more formidable than a passage to east Kent. With the prevailing winds in the eastern Channel blowing from the south-west and west – modern meteorological data show that 48% of the winds blowing in the summer months are from the westerly quadrant – the chances of a favourable wind are significantly less than for the shorter passage to east Kent. We know that Caesar exploited the tidal streams in the Dover Strait in a way that would not be possible on the longer passage to the Solent. Indeed it is very likely that a fleet sailing along the south coast could have been significantly retarded by adverse tidal streams.

Moreover, any passage made by a fleet will be much longer than the equivalent passage by a single ship. Factors such as the need to establish and maintain fleet formation, sailing at the speed of the slowest, the time needed for the fleet to leave or enter a harbour or that required to embark and disembark in good order all combine to make a significant impact on the overall fleet speed. My own assessment of these factors suggests that it would have been difficult for a Roman invasion fleet to complete the passage from Boulogne to the Solent from embarkation to disembarkation in much less than a week.

Hind had pointed to a little known invasion by the Romans in AD296 under Constantius Chlorus. Ten years earlier a rebel named Carausius had proclaimed himself emperor in Britain; the purpose of this invasion was to restore legitimate Roman rule. Part of the invasion army under Constantius's second in command, Asclepiodotus, landed in the Solent. Hind suggested that if Asclepiodotus landed here, so too might Plautius.

The invasion of 296 differed from that of 43 in two significant ways. The first was that Asclepiodotus's fleet sailed, not from Boulogne, but the Seine. That an established trade route existed between the Seine and the Solent is well attested, but there is no evidence for such a route between Boulogne and the Solent. Secondly, the strategic situation had fundamentally changed with the construction in the third century AD, along the east and south coasts of Britain, of the Saxon Shore forts. There is considerable academic uncertainty about the original purpose of these forts, but with forts at Reculver, Richborough, Dover and Lympne, in 296 there was a major deterrent to a landing in Kent. Such a deterrent did not exist in 43 and naval strategy would have argued for the short crossing.

In all I looked at 17 cross-Channel fleet operations, including the Norman invasion, the Spanish Armada and the Descent of William of Orange in 1688. Of these nine (53%) failed to reach their destination. Of seven cross-Channel passages by Caesar's fleet or parts of it, only two (29%) failed. These two failures resulted from bad weather and adverse winds and were commanded by subordinates of Caesar who were arguably under pressure from him to make the passage as soon as possible. Passages by Caesar himself on the short route between Boulogne and east Kent were 100% successful.

On the other hand perhaps the most spectacular failure was that of Duke Robert the Magnificent of Normandy. In the 1030s he assembled a fleet which set sail to invade England from Fécamp. Caught in a storm, it was driven to Jersey. Such statistics underline the sheer uncertainty of invasion passage-making in the age of sail. The Roman naval commanders of AD43 would have had a massive incentive to reduce these uncertainties by using the short crossing of the Dover Strait.

I do not pretend that the argument from naval strategy can be reconciled with Dio's description of the shooting star or with his account of the submission of the Dobunni. But it is important to bear in mind that Dio, writing in the third century, is not a primary source. In a Britannia paper in 2000, EW Black described Dio's method of working: after ten years collecting his material, he spent 12 more writing it up. In the process "there must have been scope for misunderstanding his sources, either at the time he made his original notes or when he came to make sense of them later". In an earlier contribution (1998), Black had suggested one such misunderstanding: that two battles in Dio's account, one on the unnamed river and a subsequent battle on the Thames, were in reality a single battle on the Thames, accounts of which Dio unwittingly transcribed from separate sources.

Given such uncertainties we are entitled to test what Dio tells us against other evidence, including that of archaeology and what we know of fleet operations in the Channel. Dio's knowledge of the geography of northwest Europe may have been unreliable. While he may have known from Claudius's biographer, Suetonius, that Claudius embarked at Boulogne, he may well not have been able to place Boulogne on a map. As for the Dobunni, did he really have any clear idea as to where they were settled? In view of the strength of the argument from naval strategy, it would be wrong to take these two documented incidents at face value and use them to reject the hypothesis of a landing at Richborough.

Gerald Grainge is a former local government officer, who received his doctorate at Southampton University with a thesis on the Claudian invasion's naval strategy. His book The Roman Invasions of Britain was reviewed on page 47 of this issue.

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