The brave and cautious prince Cassivellaunus, who ruled in what is now Middlesex and the surrounding district - formerly the terror of the Celts to the south of the Thames, but now the protector and champion of the whole nation - had headed the defence of the land.

He soon saw that nothing at all could be done with the Celtic infantry against the Roman, and that the mass of the general levy - which it was difficult to feed and difficult to control - was only a hindrance to the defence; he therefore dismissed it and retained only the war-chariots, of which he collected 4000, and in which the warriors, accustomed to leap down from their chariots and fight on foot, could be employed in a twofold manner like the burgess-cavalry of the earliest Rome. When Caesar was once more able to continue his march, he met with no interruption to it; but the British war-chariots moved always in front and alongside of the Roman army, induced the evacuation of the country (which from the absence of towns proved no great difficulty), prevented the sending out of detachments, and threatened the communications. The Thames was crossed - apparently between Kingston and Brentford above London - by the Romans; they moved forward, but made no real progress; the general achieved no victory, the soldiers made no booty, and the only actual result, the submission of the Trinobante in the modern Essex, was less the effect of a dread of the Romans than of the deep hostility between this canton and Cassivellaunus. The danger increased with every onward step, and the attack, which the princes of Kent by the orders of Cassivellaunus made on the Roman naval camp, although it was repulsed, was an urgent warning to turn back.

The taking by storm of a great British tree-barricade, in which a multitude of cattle fell into the hands of the Romans, furnished a passable conclusion to the aimless advance and a tolerable pretext for returning. Cassivellaunus was sagacious enough not to drive the dangerous enemy to extremities, and promised, as Caesar desired him, to abstain from disturbing the Trinobantes, to pay tribute and to furnish hostages; nothing was said of delivering up arms or leaving behind a Roman garrison, and even those promises were, it may be presumed, so far as they concerned the future, neither given nor received in earnest. After receiving the hostages Caesar returned to the naval camp and thence to Gaul. If he, as it would certainly seem, had hoped on this occasion to conquer Britain, the scheme was totally thwarted partly by the wise defensive system of Cassivellaunus, partly and chiefly by the unserviceableness of the Italian oared fleet in the waters of the North Sea; for it is certain that the stipulated tribute was never paid. But the immediate object - of rousing the islanders out of their haughty security and inducing them in their own interest no longer to allow their island to be a rendezvous for continental emigrants - seems certainly to have been attained; at least no complaints are afterwards heard as to the bestowal of such protection.

The work of repelling the Germanic invasion and of subduing the continental Celts was completed. But it is often easier to subdue a free nation than to keep a subdued one in subjection. The rivalry for the hegemony, by which more even than by the attacks of Rome the Celtic nation had been ruined, was in some measure set aside by the conquest, inasmuch as the conqueror took the hegemony to himself. Separate interests were silent; under the common oppression at any rate they felt themselves again as one people; and the infinite value of that which they had with indifference gambled away when they possessed it - freedom and nationality - was now, when it was too late, fully appreciated by their infinite longing. But was it, then, too late? With indignant shame they confessed to themselves that a nation, which numbered at least a million of men capable of arms, a nation of ancient and well-founded warlike renown, had allowed the yoke to be imposed upon it by, at the most, 50,000 Romans. The submission of the confederacy of central Gaul without having struck even a blow; the submission of the Belgic confederacy without having done more than merely shown a wish to strike; the heroic fall on the other hand of the Nervii and the Veneti, the sagacious and successful resistance of the Morini, and of the Britons under Cassivellaunus - all that in each case had been done or neglected, had failed or had succeeded - spurred the minds of the patriots to new attempts, if possible, more united and more successful. Especially among the Celtic nobility there prevailed an excitement, which seemed every moment as if it must break out into a general insurrection.

Even before the second expedition to Britain in the spring of 700 Caesar had found it necessary to go in person to the Treveri, who, since they had compromised themselves in the Nervian conflict in 697, had no longer appeared at the general diets and had formed more than suspicious connections with the Germans beyond the Rhine. At that time Caesar had contented himself with carrying the men of most note among the patriot party, particularly Indutiomarus, along with him to Britain in the ranks of the Treverian cavalry-contingent; he did his utmost to overlook the conspiracy, that he might not by strict measures ripen it into insurrection. But when the Haeduan Dumnorix, who likewise was present in the army destined for Britain, nominally as a cavalry officer, but really as a hostage, peremptorily refused to embark and rode home instead, Caesar could not do otherwise than have him pursued as a deserter; he was accordingly overtaken by the division sent after him and, when he stood on his defence, was cut down (700). That the most esteemed knight of the most powerful and still the least dependent of the Celtic cantons should have been put to death by the Romans, was a thunder-clap for the whole Celtic nobility; every one who was conscious of similar sentiments - and they formed the great majority - saw in that catastrophe the picture of what was in store for himself.

If patriotism and despair had induced the heads of the Celtic nobility to conspire, fear and self-defence now drove the conspirators to strike. In the winter of 700-701, with the exception of a legion stationed in Brittany and a second in the very unsettled canton of the Carnutes (near Chartres), the whole Roman army numbering six legions was encamped in the Belgic territory. The scantiness of the supplies of grain had induced Caesar to station his troops farther apart than he was otherwise wont to do - in six different camps constructed in the cantons of the Bellovaci, Ambiani, Morini, Nervii, Remi, and Eburones. The fixed camp placed farthest towards the east in the territory of the Eburones, probably not far from the later Aduatuca (the modern Tongern), the strongest of all, consisting of a legion under one of the most respected of Caesar's leaders of division, Quintus Titurius Sabinus, besides different detachments led by the brave Lucius Aurunculeius Cotta[43] and amounting together to the strength of half a legion, found itself all of a sudden surrounded by the general levy of the Eburones under the kings Ambiorix and Catuvolcus. The attack came so unexpectedly, that the very men absent from the camp could not be recalled and were cut off by the enemy; otherwise the immediate danger was not great, as there was no lack of provisions, and the assault, which the Eburones attempted, recoiled powerless from the Roman intrenchments.