Addenda to Julius Caesar’s Expeditions to Britain

In fact, for his first expedition, both Caesar’s port of departure in Gaul and his landing-place in Britain are uncertain. Caesar says he set out from Portus Itius on his second expedition.[*] It is often assumed that he set out from there on the first too, but Caesar gives no indication that this was the case. The location of Portus Itius is itself a subject of debate – Wissant is a strong contender, but Boulogne is the definite favourite. Actually, the general consensus seems to be that Caesar’s first expedition set out from Boulogne, regardless of whether it was Portus Itius or not. The 18 delayed transport vessels were in a harbour “8 miles off” from Caesar’s point of departure. This “upper port” may, then, have been Ambleteuse, to the north of Boulogne. At any rate, when favourable weather allowed Caesar to set sail for Britain, he despatched the cavalry to this “further port”, with instructions to “embark there, and follow him”.[*] It seems indisputable that Caesar first anchored off Dover. Various textual details strongly indicate that it was near Deal, to the north-east of Dover, that he finally landed, but there is no archaeological evidence to support this, and there is a snag.

Caesar says he “reached Britain about the fourth hour”. Daytime was divided into twelve hours – the ‘first hour’ beginning at sunrise, the ‘twelfth hour’ ending at sunset – so, the length of an hour depends on the latitude and time of year. At the time of year in question, at Dover, dawn is about 5 am (GMT) and daytime is about fourteen hours, so the fourth hour was approx. 8.30–9.40 am.  Caesar says he waited at anchor “till the ninth hour”, i.e. 2.20–3.30 pm, for the rest of the fleet to join him, but then, “getting wind and tide together in his favour”, sailed to the landing-place.[*] Now, Caesar reports that:

… four days after the expedition reached Britain, the 18 ships … which had taken the cavalry on board, sailed from the upper port with a light breeze. They were getting close to Britain and were seen from the camp, when such a violent storm arose that none of them could keep their course …

The same night it happened to be a full moon …

The Gallic War IV, 28–29

Because of Caesar’s various references to the time of year, the full moon in question has to have been on the night of 30th/31st August. Depending how the four day interval before the cavalry set off is counted, his arrival at Dover would have been on 26th or 27th August.[*] Unfortunately, on those dates, between 2.20 pm and 3.30 pm, the tidal stream would have been running westwards i.e. away from Deal. Proposals for landing sites to the west of Dover have been made, but they are difficult to reconcile with Caesar’s text. One simple solution to this conundrum would be that Caesar didn’t sail until a short while after the ninth hour (presumably, his times were only estimated from the sun’s position anyway), when the tide had changed in his favour. According to data published by T. Rice Holmes, in Ancient Britain and the Invasions of Julius Caesar (1907), the tide turned at 3.54 pm on the 26th (he suggests that the wind may have caused it to turn earlier – perhaps bringing it within the ninth hour). On the 27th, however, the tide wouldn’t turn until 5.15 pm, which, even if the wind advanced it a little, would, surely, be too late in the day for all that was yet to occur.

But, it will be objected, Caesar may have landed on the 27th of August; and in that case the stream could not have turned eastward before the close of the ninth hour. Certainly it could not have done so unless it had turned westward unusually early, or unless its westward duration had but little exceeded four hours; and although this has been shown to be within the bounds of possibility, it is to the last degree improbable. But if he landed on the 26th of August, an assumption which has been proved to be not inconsistent with his narrative, it is not improbable that the stream may have turned eastward in the ninth hour; and this is all that I am concerned at present to show.

Ancient Britain and the Invasions of Julius Caesar,
‘The Place of Caesar’s Landing in Britain’ (p.611).

Rice Holmes’ exhaustive analysis of Caesar’s campaigns in Britain still carries great weight. He was an ardent advocate of Caesar having sailed in the direction of Deal:

There is but one conclusion to which we can come, and that conclusion is absolutely certain: when Caesar weighed anchor off the Kentish cliffs, he sailed towards the north-east.

Ancient Britain and the Invasions of Julius Caesar,
‘The Place of Caesar’s Landing in Britain’ (p.649).

He examined the various solutions to the riddle of Caesar’s landing-place:

I began this inquiry early in 1900 with a mind absolutely unbiassed, resolved to do one of two things – either to solve the problem, or, if that could not be done, to show, once for all, that it was insoluble. The reader knows that I have not neglected any means of ascertaining the truth; and I have provided him with the means of controlling every statement which I have made. I have set down fully and fairly the arguments of those from whom I differ; and I have kept back nothing, I have called attention to everything. that might appear to tell against the conclusion to which the evidence inevitably led. I need not say anything by way of recapitulation, for no man who has read this article attentively can be lacking either in patience or in intelligence; and I am sure that the reader is by this time convinced of these things: that it has been demonstrated that Caesar did not land at Pevensey, or anywhere in Sussex; that it has been demonstrated that he did not land at Hythe, or anywhere in Romney Marsh; and that it has been demonstrated that he did land both in 55 and in 54 BC in East Kent – in the former year between Walmer Castle and Deal Castle, in the latter north of Deal Castle. That some will still for a time dispute these conclusions is likely enough; but not those whose judgements count. For them the problem is solved.

Ancient Britain and the Invasions of Julius Caesar,
‘The Place of Caesar’s Landing in Britain’ (p.665).

There is, however, another, perhaps more elegant, solution to the nagging ‘tide problem’ than that espoused by Rice Holmes. Possibly, an error in regard to the “four days” (diem quartum) has crept into Caesar’s text. In Roman Britain and the English Settlements (Second Edition, 1937, p.37 fn.1), R.G Collingwood comments:

I follow Rice Holmes in making Caesar land east of Dover … I suspect something has gone wrong with the numeral quartum in IV, 28 [of The Gallic War]; if the interval was more like a week, the stream would be running north-eastwards when he weighed.

Roman numerals are, indeed, notoriously fragile – easy to make errors when reading and easy to make errors when writing. Perhaps Caesar, himself, simply misread the numeral VII or VIII as IIII when transcribing his field-notes.

To generate a meaningful chronology of Caesar’s second expedition, the date references in Cicero’s letters have to be converted into modern usage. The months of July (after Julius Caesar) and August (after Augustus, the first emperor) were, of course, not used by Cicero – Quintilis was renamed July following Caesar’s assassination in 44 BC, and Sextilis was renamed August in 8 BC. The days are numbered relative to the next of three fixed monthly points: the Nones; the Ides; the Kalends of the following month. The Kalends is the 1st, the Nones is the 5th and the Ides the 13th – except in March, May, Quintilis/July and October, when the Nones is the 7th and the Ides is the 15th. For example: a.d. V Non. Quint. is the fifth day before (a.d. = ante diem = ‘days before’) the Nones of Quintilis. In Quintilis/July the Nones is the 7th, so, counting inclusively, the fifth before is the 3rd.[*] The date, then, is 3rd July – except that Caesar’s calendrical reform (the ‘Julian calendar’) was introduced on 1st January 45 BC. Applying the correction appropriate for 54 BC, the year of Caesar’s second expedition, produces the final result: 8th June.[*]

In his Ancient Britain and the Invasions of Julius Caesar (1907), T. Rice Holmes outlined the process by which he calculated the date of Caesar’s arrival in Britain:

On the 27th of July, that is to say, on the 2nd of July of the Julian calendar, Cicero wrote to Atticus, “Judging from my brother Quintus’s letters, I imagine that by this time he is in Britain” [Letters to Atticus IV, 15] … It would be very rash, however, to infer from this that Caesar landed in Britain before, or even as early as, the 2nd of July; for, as we have seen, his embarkation was delayed by the long continuance of adverse winds. The first letter which announced the arrival of the expeditionary force in Britain was referred to by Cicero in a letter to Quintus, in which he says, “How I rejoiced at your letter from Britain! I was nervous about the sea and the coast of that island” [Letters to his Brother Quintus II, 15] … This letter is undated; but it must have been written some time after the one which Cicero wrote to Atticus on the 27th of July; for in the letter to Atticus we find the words, “I have undertaken to defend Messius … After that I have to prepare myself for Drusus, and then for Scaurus” … while in the letter to Quintus Cicero wrote, “The day I write this Drusus has been acquitted … The comitia have been put off to September. Scaurus’s trial will take place immediately” … Asconius tells us that the last day of Scaurus’s trial was the 2nd of September[*]; and Cicero’s remark that “the comitia have been put off to September” makes it evident that he wrote in August; while from his saying that “Scaurus’s trial will take place immediately” we should naturally infer that when he wrote the 2nd of September was not far off. Letters from Britain generally reached Rome in about 27 days[*]; and accordingly we may conclude that the letter in which Quintus Cicero announced his arrival in Britain was written about the end of July; that is to say, about the 6th of July of the Julian calendar. —

— Now Caesar says that the tide [in the Straits of Dover] turned westward soon after daybreak on the morning of his arrival in Britain [The Gallic War V, 8]; and this statement proves that he landed either about the time of full moon or about the time of new moon. There was a full moon on the 21st of July, 54 BC; and the previous new moon occurred on the 7th of July. [Here, Rice Holmes refutes the theory that “the landing must have taken place on the day of full moon”, proposed by Napoleon III.] … If, then, we decide that Caesar landed in Britain on the day of new moon, the 7th of July, 54 BC, we shall not be more than one day wrong; but to fix the date with absolute precision is impossible.
As Caesar landed about the 7th of July, it follows that he had reached the Portus Itius, where he was delayed about 25 days, about the 11th of June.

Ancient Britain and the Invasions of Julius Caesar,
‘The Julian Calendar and the Chronology of Caesar’s Invasions of Britain’ (pp.728–30).

Concerning the date of Caesar’s departure from Britain:

We have seen that on the 25th of September (the 29th of August of the Julian calendar) he [Caesar] wrote to Cicero, saying that he was on the point of bringing back the army [Letters to Atticus IV, 18]… On the whole, it appears to me that all we can say for certain regarding the date of Caesar’s return is this. It cannot be fixed earlier than several days after the 29th of August of the Julian calendar … Bearing in mind that it occurred when “the equinox was at hand” [The Gallic War, 23], we may place it about the middle of September.

Ancient Britain and the Invasions of Julius Caesar,
‘The Julian Calendar and the Chronology of Caesar’s Invasions of Britain’ (pp.734–5).