The name Alamanni, German for "all men", clearly shows that there was a group that was recognized as a group by the Germanic-speaking people beyond the Roman frontier, but it is not clear what is meant. They appear for the first time during a campaign by the emperor Caracalla, who passed through the gate of Dalkingen and won a military victory (213 CE).note[Cassius Dio, Roman History 78.13.4-7; Historia Augusta, Caracalla 10.5.]
Later, after the Romans had retreated from the Black Forest and had taken the Middle Danube and Upper Rhine as frontier, the name Alamanni is used for all inhabitants of the abandoned part of the Roman Empire, the Agri Decumates. It is clear, however, that there were several ethnic units living in this area, which included people once known as Suebi and others. The army of Chnodomar, who defeated by the Roman general Julian (the future emperor) in the battle of Argentoratum (357). had several Germanic tribal leaders in his army. One of them, Marcianus, is later mentioned as a dangerous enemy of Valentinian I, but appears to have been in control of a small area only. In short, the name, whatever its original meaning, was used for all ethnic groups in the former Agri Decumates, both for the unity and for the independent tribes.
The relations with Rome could be good or bad, but of course the latter situates dominates in our sources. Various battles were fought in Gaul and northern Italy; there is also archaeological evidence for destruction, especially in the third quarter of the third century. Still, many people in the Black Forest were descendants of the original Roman population and must have felt that they were just Romans living outside the line of forts. Often, relations were friendly.
In the fifth century, Alamanni penetrated the Alsace and Helvetia. They were defeated by the Frankish king Clovis in the battle of Tolbiac (c.496) and became part of the Frankish kingdom.