During the short part of the summer which remained he resolved to proceed into Britain, because succours had been constantly furnished to the Gauls from that country. He thought it expedient, if he only entered the island, to see into the character of the people, and to gain knowledge of their localities, harbours, and landing-places. Having collected about eighty transport ships, he set sail with two legions in fair weather, and the soldiers were attacked instantly on landing by the cavalry and charioteers of the barbarians. The enemy were vanquished, but could not be pursued, because the Roman horse had not been able to maintain their course at sea and to reach the island. This alone was wanting to Cæsar's accustomed success. _V.--Cæsar on the Thames_ During the winter Cæsar commanded as many ships as possible to be constructed, and the old repaired. About six hundred transports and twenty ships of war were built, and, after settling some disputes in Gaul among the chiefs, Cæsar went to Port Itius with the legions. He took with him several of the leading chiefs of the Gauls, determined to retain them as hostages and to keep them with him during his next expedition to Britain, lest a commotion should arise in Gaul during his absence. Cæsar, having crossed to the shore of Britain and disembarked his army at a convenient spot advanced about twelve miles and repelled all attacks of the cavalry and charioteers of the enemy. Then he led his forces into the territories of Cassivellaunus to the River Thames, which river can be forded in one place only. Here an engagement took place which resulted in the flight of the Britons. But Cassivellaunus had sent messengers to the four kings who reigned over Kent and the districts by the sea, Cingetorix, Carvilius, Taximaquilus, and Segonax, commanding them to collect all their forces and assail the naval camp. In the battle which ensued the Romans were victorious, and when Cassivellaunus heard of this disaster he sent ambassadors to Cæsar to treat about a surrender. Cæsar, since he had resolved to pass the winter on the continent, on account of sudden revolts in Gaul, demanded hostages and prescribed what tribute Britain should pay each year to the Roman people. Cæsar, expecting for many reasons greater commotion in Gaul, levied additional forces. He saw that war was being prepared on all sides, that the Nervii, Aduatuci, and Menapii, with the addition of all the Germans on this side of the Rhine, were under arms; that the Senones did not assemble according to his command, and were concerting measures with Carnutes and the neighbouring states; and that the Germans were importuned by the Treviri in frequent embassies. Therefore he thought that he ought to take prompt measures for the war.