The Alemanni crossed the frozen Rhine in large numbers and invaded the Roman Empire.
The Alemanni or Alamanni, were a confederation of Germanic tribes on the Upper Rhine River. First mentioned by Cassius Dio in the context of the campaign of Caracalla of 213, the Alemanni captured the Agri Decumates in 260, and later expanded into present-day Alsace, and northern Switzerland, leading to the establishment of the Old High German language in those regions, by the eighth century named Alamannia.