Battle of Alesia
Caesar engaged in the Gallic Wars (58–50 BC), which led to his conquest of Gaul beyond Gallia Narbonensis. When the Helvetii, a federation of tribes from what is now Switzerland, planned a migration to the Atlantic coast through Gaul, Caesar went to Geneva and forbade the Helvetii to move into Gaul. While he went to Gallia Cisalpina to collect three other legions, the Helvetii attacked the territories of the Aedui, Ambarri, and Allobroges, three Gallic tribes, which called for Caesar’s help. Caesar and his Gallic allies defeated the Helvetii. The Gallic tribes then asked for Caesar to intervene against an invasion by the Suebi, a Germanic tribe. Caesar defeated the Suebi. In 57 BC he intervened in intra-Gallic conflicts and marched on the Belgae of northern Gaul. From then on he conquered the Gallic peoples one by one. His successes in Gaul brought Caesar political prestige in Rome and great wealth through the spoils of wars and the sale of war captives as slaves.
Colonia Claudia Ara Agrippinensium
In AD 260 Postumus made Cologne the capital of the Gallic Empire, which included the German and Gallic provinces, Britannia and the provinces of Hispania. The Gallic Empire lasted only fourteen years. By the 3rd century, only 20,000 people lived in and around the town as the city was badly affected by the crisis of the 3rd century. In AD 310, Emperor Constantine I had a bridge over the Rhine constructed; this was guarded by the "castellum" Divitia (nowadays "Deutz"). In AD 321 Jews are documented in Cologne; when exactly the first Jews arrived in the Rhineland area cannot be established any more, but the Cologne community claims to be the oldest north of the Alps.