After Varus' defeat in Germania in the 1st century, Rome had adopted a largely defensive strategy along the border with Germania, constructing a line of defences known as "limes" along the Rhine. Although the exact historicity is unclear, since the Romans often assigned one name to several distinct tribal groups, or conversely applied several names to a single group at different times, some mix of Germanic peoples, Celts, and tribes of mixed Celto-Germanic ethnicity were settled in the lands of Germania from the 1st century onwards. The Cherusci, Bructeri, Tencteri, Usipi, Marsi, and Chatti of Varus' time had by the 3rd century either evolved into or been displaced by a confederacy or alliance of Germanic tribes collectively known as the Alamanni, first mentioned by Cassius Dio describing the campaign of Caracalla in 213 AD.