The Roman expansion brought the defeat of the Allobrogi in 121 BC and during the Gallic Wars in 58 BC Julius Caesar overcame the Helvetii. The Rhaetians continued to resist but were eventually conquered when the Romans turned northward to the Danube valley in Austria and defeated the Brigantes. The Romans built settlements in the Alps; towns such as Aosta (named for Augustus) in Italy, Martigny and Lausanne in Switzerland, and Partenkirchen in Bavaria show remains of Roman baths, villas, arenas and temples. Much of the Alpine region was gradually settled by Germanic tribes, (Lombards, Alemanni, Bavarii, and Franks) from the 6th to the 13th centuries mixing with the local Celtic tribes.

What brought the defeat of the Allobrogi?