being used by cantons themselves banding together for purposes of supporting a citizen army (the "war bands"). Concentration of Germanic peoples under Ariovistus The term Suebi has a double meaning in the sources. On the one hand Tacitus' Germania tells us (Chapters 38, 39) that they occupy more than half of Germany, use a distinctive hairstyle, and are spiritually centered on the Semnones. On the other hand, the Suebi of the upper Danube are described as though they were a tribe. The solution to the puzzle as well as explaining the historical circumstances leading to the choice of the Agri Decumates as a defensive point and the concentration of Germans there are probably to be found in the German attack on the Gallic fortified town of Vesontio in 58 BC. The upper Rhine and Danube appear to form a funnel pointing straight at Vesontio. Julius Caesar in Gallic Wars tells us (1.51) that Ariovistus had gathered an army from a wide region of Germany, but especially the Harudes, Marcomanni, Triboci, Vangiones, Nemetes and Sedusii. The Suebi were being invited to join. They lived in 100 cantons (4.1) from which 1000 young men per year were chosen for military service, a citizen-army by our standards and by comparison with the Roman professional army. Ariovistus had become involved in an invasion of Gaul, which the German wished to settle. Intending to take the strategic town of Vesontio, he concentrated his forces on the Rhine near Lake Constance, and when the Suebi arrived, he crossed. The Gauls had called to Rome for military aid. Caesar occupied the town first and defeated the Germans before its walls, slaughtering most of the German army as it tried to flee across the river (1.36ff). He did not pursue the retreating remnants, leaving what was left of the German army and their dependents intact on the other side of the Rhine. The Gauls were ambivalent in their policies toward the Romans. In 53 BC the Treveri broke their alliance and attempted to break free of Rome. Caesar foresaw that they would now attempt to ally themselves with the Germans. He crossed the Rhine to forestall that event, a successful strategy. Remembering their expensive defeat at the Battle of Vesontio, the Germans withdrew to the Black Forest, concentrating there a mixed population dominated by Suebi. As they had left their tribal homes behind, they probably took over all