he year ad 9 did not go well for the Roman empire. Three legions, six auxiliary cohorts and attached cavalry—roughly 20,000 troops—under Publius Quinctilius Varus sought to extend Roman control deep into Germany. In the Teutoburg Forest, near present-day Osnabrück, allied Germanic tribes under Arminius ambushed and annihilated the legions. The empire struck back hard between ad 14 and 16. Operating from bases west of the Rhine River, legions under Germanicus
