To which event where three Roman legions were distroyed is the phrase The German Forest sometimes used to refer to?
German Forest:  It was also used with reference to historical or legendary events in German forests, such as Tacitus' description of the Battle of the Teutoburg Forest or even the nature mysticism of the stylized Germanic national myth, the "Nibelungenlied" as the history of its multi-faceted reception shows. Battle of the Teutoburg Forest: The Battle of the Teutoburg Forest (German: "Schlacht im Teutoburger Wald" , "Hermannsschlacht", or "Varusschlacht"), described as the Varian Disaster ("Clades Variana") by Roman historians, took place in the Teutoburg Forest in 9 CE, when an alliance of Germanic tribes ambushed and decisively destroyed three Roman legions and their auxiliaries, led by Publius Quinctilius Varus.
Battle of the Teutoburg Forest