They found in Hermann a leader of extraordinary bravery and resource. He laid his plans with the chiefs of the Catti, Bructeri, and other tribes that lived between the Rhine and the Albis (Elbe), some of which broke out into insurrection. Hermann then offered Varus his assistance in reducing them to subjection, and thus led him to advance some distance from the Rhine into the interior. Varus began his march with three legions, six cohorts, and a body of cavalry, and Hermann served him as a guide through the wilds. The Romans were thus drawn into an ambuscade in the Teutoburg forest, and found themselves all at once surrounded by numerous bodies of Germans, who were directed by himself. The Romans fought desperately; but being unacquainted with the localities, and unable to form their ranks owing to the thickness of the forests and the marshy nature of the ground, they were defeated after a three days' battle, by the Germans, who destroyed them in detail. At last, Varus, being wounded and seeing no chance of escape, fell upon his sword, and the other chief officers followed his example.

The legions were entirely destroyed, and the cavalry alone cut their way through the enemy and regained the banks of the Rhine. By this defeat the Romans lost all their conquests beyond that river; and although Germanicus some years after again carried their arms to the Weser, they never established anything like a solid dominion over those regions. The defeat of Varus occurred, according to various chronologists, in the year 763 of Rome (A. D. 9). The scene of the defeat is conjectured to have been in the country of the Bructeri, near the sources of the Ems and the Lippe. The news of this calamity, the greatest that had befallen the Roman arms since the defeat of Crassus, was received with universal amazement and terror. The despairing cry of Augustus, "Varus, Varus, give me back my legions!" testified to the consternation even at Rome, where it was expected that the barbarians would take a terrible revenge for the wrongs they had suffered.

The fears of invasion, however, were not realized. L. Asprena guarded the banks of the Rhine, and the Germans were too little united among themselves to attack the Empire. Augustus in the following year sent Tiberius to the Rhine with a fresh army; but he does not seem to have effected anything of importance. Hermann meantime quarrelled with Segestes, chief of the Catti, whose daughter Tusnelda, he had carried off and married against her father's consent. When Germanicus, after the death of Augustus, marched into the interior of Germany to avenge the defeat of Varus, he was assisted by Segestes, and also by the Chauci and other tribes. In the first battle against Hermann, his wife Tusnelda, was taken prisoner by the Romans, and she afterward figured in the triumph of Germanicus. Germanicus, having reached the scene of Varus's defeat, paid funeral honors to the remains of the legions; but Hermann, who was hovering about his line of march, without coming to a pitched battle, harassed him in his retreat, and occasioned a great loss to Cæcina, the lieutenant of Germanicus.

In the following year, Germanicus advanced again as far as the Visurgis, or Weser, where he found Hermann encamped ready for battle. A desperate fight took place, in which Hermann, after performing prodigies of valor, was defeated, and escaped with difficulty. But the victory was gained at such cost that Germanicus and his army had to take refuge in their ships, nor did the Romans ever again attempt the conquest of the fiercer German tribes.

When Tiberius recalled Germanicus, he observed that the Cherusci, Bructeri, and other unsubdued tribes, might be left to their own internal dissensions. He seems to have guessed right.

No sooner had the Romans been driven off, than Hermann had to protect his people against an internal danger. Maroboduus, the chief of the Marcomanni, a man of great ambition, had by treachery or by open fighting, made himself master of several neighboring tribes. Hermann began to fear his designs, and after the defeat of Varus, warned him of his peril by sending him the Roman general's head. When Germanicus finally left the country, Hermann declared war against Maroboduus, and, being joined by the Semnones and Longobards, defeated him on the borders of the Hercynian forest, broke up his kingdom, and drove him from Germany. The fugitive applied to Rome for assistance. Tiberius then sent his son Drusus into the Illyricum; but the Romans did not advance beyond the Danube, and Hermann remained unmolested in Northern Germany. Shortly after, however, Hermann was killed by his own relatives, being accused, as it would seem, of aspiring to absolute dominion. He died at the age of thirty-seven, in the twenty-first year of our era, after being for twelve years the leader and champion of Germany.