The ethnogenesis of the Germanic tribes is assumed to have occurred during the Nordic Bronze Age, or at the latest, during the Pre-Roman Iron Age. From southern Scandinavia and northern Germany, the tribes began expanding south, east and west in the first century BC, coming into contact with the Celtic tribes of Gaul and Iranian, Baltic, and Slavic tribes in Eastern Europe. Little is known about early Germanic history, except through their interactions with the Roman Empire and archaeological finds.

Under Augustus, the Roman General Publius Quinctilius Varus began to invade Germany, and it was in this period that the German tribes became familiar with Roman tactics of warfare while maintaining their national identity. In AD 9, three Roman legions led by Publius Quinctilius Varus were crushed by the Cheruscan leader Arminius (Hermann) in the Battle of the Teutoburg Forest. Germany, as far as the Rhine and the Danube, thus remained outside the Roman Empire. By AD 100, the time of Tacitus' Germania, Germanic tribes settled along the Rhine and the Danube (the Limes Germanicus), occupying most of the area of modern Germany. The 3rd century saw the emergence of a number of large West Germanic tribes: Alamanni, Franks, Chatti, Saxons, Frisians, Sicambri, and Thuringii. Around 260, the Germanic peoples broke through the Limes and the Danube frontier.