It was not enough to have driven the Germans out of Gaul. Caesar respected their character. He admired their abstinence from wine, their courage, their frugal habits, and their pure morality. But their virtues made them only more dangerous; and he desired to show them that the Roman arm was long and could reach them even in their own homes. Parties of the late invaders had returned over the Rhine, and were protected by the Sigambri in Westphalia. Caesar had demanded their surrender, and the Sigambri had answered that Roman authority did not reach across the river; if Caesar forbade Germans to cross into Gaul, the Germans would not allow the Romans to dictate to them in their own country. The Ubii were growing anxious. They were threatened by the Sueves for deserting the national cause. They begged Caesar to show himself among them, though his stay might be but short, as a proof that he had power and will to protect them; and they offered him boats and barges to carry his army over. Caesar decided to go, but to go with more ostentation. The object was to impress the German imagination; and boats and barges which might not always be obtainable would, if they seemed essential, diminish the effect. The legions were skilled workmen, able to turn their hand to anything. He determined to make a bridge, and he chose Bonn for the site of it. The river was broad, deep, and rapid. The materials were still standing in the forest; yet in ten days from the first stroke that was delivered by an axe, a bridge had been made standing firmly on rows of piles with a road over it forty feet wide. A strong guard was left at each end. Caesar marched across with the legions, and from all sides deputations from the astonished people poured in to beg for peace. The Sigambri had fled to their woods. The Suevi fell back into the Thuringian forests. He burnt the villages of the Sigambri, to leave the print of his presence. He paid the Ubii a long visit; and after remaining eighteen days beyond the river, he considered that his purpose had been gained, and he returned to Gaul, destroying the bridge behind him.