In the following year (B.C. 55) Northern Gaul was disturbed by another great movement of population. Two German tribes, themselves dispossessed by the overpowering strength of the Suebi, a great confederation of kindred tribes from Eastern Germany, crossed the Rhine, and quartered themselves on the Menapii, a people which inhabited the left bank of the lower Rhine. Cæsar was well aware that the ill-affected Gauls would soon make common cause with the new-comers, and determined to be beforehand with his enemies of either race. He marched with great promptitude against them, not allowing himself to be put off by the negotiations which they desired or pretended to open with him. Before long a treacherous attack, made by the German horsemen on Cæsar's cavalry--chiefly composed, it would seem, of native levies--gave him an excellent justification for acting. He attacked the enemy, and drove them in headlong flight to the river. Many were slain in the fight and the pursuit, more were drowned in the river; the result was the almost entire destruction of the invading host. Nor did this satisfy him. He determined to make a demonstration of his strength in Germany itself. To do this he had to transport his army across the Rhine. To carry them over in boats did not, as he puts it, suit the dignity of the Roman people. Possibly he thought it unsafe. Accordingly he built a bridge, a marvel of engineering skill, when we consider the breadth, depth, and force of the river to be spanned, and the short supply of tools and materials at hand. The work was complete in ten days; eighteen days more were spent in Germany. And Cæsar then came back, having certainly impressed the tribes beyond the Rhine with a great idea of his resources. Late in this year Cæsar made his first expedition to Britain. Of this and of the more serious invasion of the following year I shall have to speak elsewhere. The year 54 B.C. was a very critical time. Cæsar evidently had overrated the result of his successes, a pardonable error, so rapid and apparently so complete had they been. A feeling of false security had suggested the somewhat romantic expedition to Britain, an expedition which he certainly would not have made if he had been aware of the real state of affairs in Gaul. He supposed that the country had been finally subdued--"pacified" or "quieted" was the Roman euphemism--but he was rudely undeceived. Fortunately for him he was in Gaul when the formidable rising, which he had soon to crush, took place. If he had been still in Britain, or if, as had been his intention, he had started for the south, the consequences might have been more serious than they were.