The visits of Cæsar to Britain, though highly interesting in more ways than one, may be briefly passed over. He came for the first time not long before the end of the campaigning season in 55 His chief reason, as he states it himself, was that he found that the Britons were in the habit of helping their neighbours of Gaul. (The inhabitants of south-eastern England were of the same race as the Belgæ.) We do not find, as a matter of fact, any mention of British auxiliaries in the Gallic armies, or that in later years Gaul was tempted into rebellion by the knowledge that Britain was free. Cæsar was of the Alexander type, strongly moved by the ambition of a conqueror. The first visit lasted altogether about three weeks, and the army practically remained where it landed.

The second visit took place in the following year (54 ) and was a far more important affair. Cæsar's intention was, we may be sure, to conquer the island. Probably he was not acquainted with its real dimensions, and circumstances occurred that made him change his plans. Originally, however, he had in his mind something more than a reconnaisance in force. He brought with him six legions and 2,000 cavalry, more than a half of his whole available force, coming at the end of July, and leaving about the middle of September. He advanced some sixty or seventy miles into the country, crossing the Thames, possibly near Weybridge, possibly a little below Eton. The Britons could not, of course, stand against him in the field, but they proved themselves to be formidable enemies. Cæsar does not expressly say that he had underrated the difficulties of the task; but he acted as if he had. He was engaged in Gaul for five more years, and during the last two of these five was practically master of the country, but he seems to have entirely abandoned the idea of subjugating Britain.

For 89 years the island was left practically to itself. Augustus, in the scroll of his achievements which he inscribed on a slab in a temple at Ancyra (the capital of the Roman province of Galatia) mentions the tribute paid by certain British kings; the inscription is imperfect at this place, and we know no particulars. It is certain, however, that no serious attempt was made on Britain between the years 54 and 43 There are various allusions to the people in the literature of the time, but they are always spoken of as savage enemies of whom very little was known.

In 43 , however, Rome, at the invitation of a native prince, who conceived himself to have suffered wrong, seriously undertook the conquest of the Island. Aulus Plautius was appointed to the command, took four legions with him, and in the course of the year the Emperor himself (Claudius) brought over an additional force. A great battle was fought near Camalodunum (Colchester), in which the Britons were, as usual, defeated. Vespasian, afterwards Emperor, was actively engaged in the west of the Island. We know very little of the details of the campaigns which followed. One heroic figure, however, stands prominently out. This is Caractacus (Caradoc). For seven years this prince (elder son of Cunobelin, the Cymbeline of Shakespeare) held out against the Roman forces. We cannot identify the scene of the final battle, but a sufficiently clear description of it has been preserved. The Britons occupied a hill which had an unfordable river in front, and was itself fortified, wherever the ground permitted or required it, with ramparts of stones. So formidable did the position, crowded as it was with warriors, seem to the Roman general, that he was inclined to manœuvre, probably to attempt a flanking movement. But the soldiers demanded to be led to a frontal attack, and their general yielded. The river was crossed, how we are not told. The space between the river and the British ramparts was not traversed without loss. Many were wounded and some killed by a storm of missiles from the British lines. But when the testudo  was formed under the rampart, rudely constructed of uncemented stones, the battle was practically over. The rampart was soon pulled down, and the Britons retired to the heights. Here they were outmatched. The artillery played upon them from a distance, and they had nothing wherewith to reply to it. In close combat the armour and weapons of the legions gave them an immense advantage. Finally the Britons were driven headlong from their position. Caractacus' wife and daughter were captured, and his brothers surrendered themselves. The king himself was handed over to his enemies by the treachery of a neighbouring potentate, Queen Cartismandua. The story of his dignified behaviour before Claudius, and of the generous spirit with which it was taken, need not be repeated here. Roman manners had been somewhat softened since the days when the brave Vercingetorix had been put to death. It was not that Caractacus had ceased to be formidable; he was never allowed to return to Britain.

Nor need I tell in detail the story of the revolt of Boadicea, Queen of the Iceni, a tribe of Eastern Britain. It was provoked by the insolence of Roman officials and the greed of Roman financiers, and for a time it shook the Roman power in Britain to its base. Londinium, already the largest and wealthiest town in Britain, though not ranking as a colony, was sacked; so was Verulamium (St. Alban's) and other places. As many as seventy thousand persons are said to have perished. The majority must have been Britons, "friendly natives," as we should now call them; but there were many Italians among them. "Citizens and allies" is the historian's term. As only seventeen years had passed since the conquest of Britain had commenced, it is remarkable how far the Romanising of the country had proceeded. Traders and settlers must have swarmed into it, as they do in the United States when an Indian reserve is thrown open. Besides these frightful massacres, there were military disasters. One legion was cut to pieces. The commander of another was so cowed that he did not venture out of his camp. But Paulinus, the commander-in-chief, behaved with consummate discretion. He refused to risk a battle with insufficient forces, though his delay meant the destruction of London. But when he struck he struck with terrific force. The British army was practically annihilated. In Southern Britain, at least, the dominion of Rome was never seriously threatened for many years after the great victory won by Paulinus.

When, in 78, Agricola took over the command of Britain, it was in North Wales that he carried on his first campaign. The campaigns that followed I need not describe in detail. The last of them was finished by a great victory over the Caledonians near the Grampians, probably at Aberfoyle, in Perthshire. The Roman sway, however, did not really extend so far. Its high-water mark was, probably, reached about 200, when the Emperor Septimius Severus marched to the extreme north of the Island, and on his return added a second wall to the great rampart constructed by Antoninus Pius between the estuaries of the Forth and the Clyde. But this advanced post was not long held. The most permanent, as it was the most elaborate barrier against the northern tribes, was the Great Wall built by Hadrian, about 120, between the Solway Firth and Newcastle-on-Tyne. Britain south of this was completely Latinised. But the existence of the walls and the fact that the Island had the reputation of being to the Empire what India is to us, a nursery of captains, prove that the North was practically independent. Here then—and this is what makes Britain really important in Roman history—was the furthest limit of Roman advance. And it was here that the first overt confession of weakness had to be made. In 408 one of the many soldiers of fortune who attempted to seize the Imperial throne crossed over into Gaul with the British legions. The legions never came back, and Britain, though nominally included in the Provinces of the Empire, was actually abandoned.