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.
Anglo-Saxon settlement of Britain
The Chronica Gallica of 452 records for the year 441: "The British provinces, which to this time had suffered various defeats and misfortunes, are reduced to Saxon rule." The Chronicle was written some distance from Britain. There is uncertainty about precise dates for fifth-century events especially before 446. This, however, does not undermine the position of the Gallic Chronicles as a very important contemporary source, which suggests that Bede's later date for 'the arrival of the Saxons' was mistaken. In the Chronicle, Britain is grouped with four other Roman territories which came under 'Germanic' dominion around the same time, the list being intended as an explanation of the end of the Roman empire in the west. The four share a similar history, as they were all given into the "power of the barbarians" by Roman authority: three were deliberately settled with German federates and though the Vandals took Africa by force their dominion was confirmed by treaty.