In 5 BC the Roman knowledge concerning the North and Baltic Sea was fairly extended during a campaign by Tiberius, reaching as far as the Elbe: Plinius describes how Roman naval formations came past Heligoland and set sail to the north-eastern coast of Denmark, and Augustus himself boasts in his "Res Gestae": "My fleet sailed from the mouth of the Rhine eastward as far as the lands of the Cimbri to which, up to that time, no Roman had ever penetrated either by land or by sea...". The multiple naval operations north of Germania had to be abandoned after the battle of the Teutoburg Forest in the year 9 AD.