In 55 B.C. Cæsar was very active in Belgic Gaul. He had swept the Teutonic hordes which had invaded Gaul in the winter back into Germania with frightful slaughter, not without treachery on his part; he had bridged the Rhine, and displayed the Eagles in a long raid on its eastern bank. This had occupied him until late in the summer. Then, as he says, it occurred to him that the short remainder of the campaigning season might be utilized for an expedition to Britain for the purpose of collecting useful information--in short, for what in modern military parlance would be termed a reconnaissance in force. It does not appear that he had anything further in mind. Later on he tells us that he had no intention of making a long stay, and he took only a few days’ provisions. Moreover, the time was too short for collecting anything like the number of ships required for the transportation of several legions. Nevertheless, the concentration of the Roman Army of Gallia on the coast opposite Dover was an event which could not but alarm the Britons, and, while Cæsar was completing his arrangements, some of their tribes sent over envoys. Presumably, the idea was that by making a nominal submission the invasion might be averted. Cæsar, however, quietly observed that he would visit them at home in a few days, and sent them back with, as his personal emissary, Commius the Atrebatian. Commius had instructions to use his influence to bring about a general submission, but his British companions made him prisoner immediately upon landing. Cæsar meanwhile was collecting Gallic merchant-ships for the transit, and had sent a trusted officer, Gaius Volusenus, with a galley, to reconnoitre for landing-places. The haste and incompleteness of his preparations were so far of slight account, since, though the Britons were determined on resistance, there was no time to form a confederacy. Caswallon (Cassivellaunus), king of the Catuvellauni, the most powerful chieftain of Britain, was endeavouring to coerce the Trinobantes; the attack would be met by the local tribal levies only.