Between September 9 and 11 in the year 9 A.D., Roman general Publius Quinctilius Varus managed to lose three full Roman legions—Legio XVII, XVIII, and XIX—to the German tribes under Arminius in the Battle of Teutoburg Forest.
The Roman legions were ambushed on the march, in crappy weather, in a heavily forested area on muddy ground, while stretched out in marching order over ten miles or more. Unable to fight in the customary order of battle as cohesive large units, they were overcome piecemeal in a classic example of a defeat in detail.
The Roman Army never again raised legions with the same numbers, retiring the “unlucky” numbers of the Varus legions permanently—an unprecedented act in Roman history. As a result of the battle, Rome permanently gave up attempts for direct control of Germania east of the Rhine, leaving the Germans alone to develop their horrid, guttural language, and culinary abominations such as liverwurst and Drecksack.