Gallia Belgica in the context of "Carausius"

Gaul (Latin: Gallia) was a region of Western Europe first clearly described by the Romans, encompassing present-day France, Belgium, Luxembourg, and parts of Switzerland, the Netherlands, Germany, and Northern Italy. It covered an area of 494,000 km (191,000 sq mi). According to Julius Caesar, who took control of the region on behalf of the Roman Republic, Gaul was divided into three parts: Gallia Celtica, Belgica, and Aquitania. Archaeologically, the Gauls were bearers of the La Tène culture during the 5th to 1st centuries BC. This material culture was found throughout Gaul and as far east as modern-day southern Poland, Slovakia, and Hungary.

Warbands led by the Gaul Brennos sacked Rome in 387 BC, becoming the only time Rome was conquered by a foreign enemy in 800 years. However, Gallia Cisalpina was conquered by the Romans in 204 BC and Gallia Narbonensis in 123 BC. Gaul was invaded after 120 BC by the Cimbri and the Teutons, who were in turn defeated by the Romans by 103 BC. Julius Caesar finally subdued the largest part of Gaul in his campaigns from 58 to 51 BC. Roman control of Gaul lasted for five centuries, until the last Roman rump state, the Domain of Soissons, fell to the Franks in AD 486.

Frankish (reconstructed endonym: *Frankisk), also known as Old Franconian or Old Frankish, was the West Germanic language spoken by the Franks from the 5th to 10th centuries.

Franks under King Chlodio settled in Roman Gaul in the 5th century. One of his successors, named Clovis I, took over the Roman province of Gallia Lugdunensis (in modern day France). Outnumbered by the local populace, the ruling Franks there adapted to its language which was a Proto-Romance dialect. However, many modern French words and place names are still of Frankish origin.

The Britons (*Pritanī, Latin: Britanni, Welsh: Brythoniaid), also known as Celtic Britons or ancient Britons, were the Celtic people who inhabited Great Britain from at least the British Iron Age until the High Middle Ages, at which point they diverged into the Welsh, Cornish, and Bretons (among others). They spoke Common Brittonic, the ancestor of the modern Brittonic languages.

The earliest written evidence for the Britons is from Greco-Roman writers and dates to the Iron Age. Ancient Britain was made up of many tribes and kingdoms, associated with various hillforts. The Britons followed an ancient Celtic religion overseen by druids. Some of the southern tribes had strong links with mainland Europe, especially Gaul and Belgica, and minted their own coins. The Roman Empire conquered most of Britain in the 1st century AD, creating the province of Britannia. The Romans invaded northern Britain, but the Britonnic tribes such as the Caledonians and Picts in the north remained unconquered, and Hadrian's Wall which bisects modern Northumbria and Cumbria became the edge of the empire. A Romano-British culture emerged, mainly in the southeast, and British Latin coexisted with Brittonic. It is unclear what relationship the Britons had with the Picts, who lived outside of the empire in northern Britain; however, most scholars today accept the fact that the Pictish language was closely related to Common Brittonic.

Clovis I (Latin: Chlodovechus; reconstructed Frankish: *Hlodowig; German: Chlodwig; c. 466 – 27 November 511) was the first king of the Franks to unite all of the Franks under one ruler, changing the form of leadership from a group of petty kings to rule by a single king, and ensuring that the kingship was passed down to his heirs. He is considered to have been the founder of the Merovingian dynasty, which ruled the Frankish kingdom for the next two centuries. Clovis is important in the historiography of France as "the first king of what would become France."

Clovis succeeded his father, Childeric I, as a king of the Salian Franks in 481, and eventually came to rule an area extending from what is now the southern Netherlands to northern France, corresponding in Roman terms to Gallia Belgica (northern Gaul). At the Battle of Soissons (486), he established his military dominance of the rump state of the fragmenting Western Roman Empire, which was then under the command of Syagrius. By the time of his death in 511, Clovis had conquered several smaller Frankish kingdoms in the northeast of Gaul, stretching into what is now Germany. Clovis also conquered the Alemanni in eastern Gaul and the Visigothic kingdom of Aquitania in the southwest. These campaigns added significantly to Clovis's domains and established his dynasty as a major political and military presence in western Europe.

The Helvetii (Ancient Greek: Ἐλουήτιοι, Latin: Helvētiī [hɛɫˈweːti.iː], Gaulish: *Heluētī), anglicized as Helvetians, were a Celtic tribe or tribal confederation occupying most of the Swiss plateau at the time of their contact with the Roman Republic in the 1st century BC. According to Julius Caesar, the Helvetians were divided into four subgroups or pagi. Of these, Caesar names only the Verbigeni and the Tigurini, while Posidonius mentions the Tigurini and the Tougeni (Τωυγενοί). They feature prominently in the Commentaries on the Gallic War, with their failed migration attempt to southwestern Gaul (58 BC) serving as a catalyst for Caesar's conquest of Gaul.

The Helvetians were subjugated after 52 BC, and under Augustus, Celtic oppida, such as Vindonissa or Basilea, were re-purposed as garrisons. In AD 68, a Helvetian uprising was crushed by Aulus Caecina Alienus.The Swiss plateau was at first incorporated into the Roman province of Gallia Belgica (22 BC), later into Germania Superior (AD 83).The Helvetians, like the rest of Gaul, were largely Romanized by the 2nd century. In the later 3rd century, Roman control over the region waned, and the Swiss plateau was exposed to the invading Alemanni. The Alemanni and Burgundians established permanent settlements in the Swiss plateau in the 5th and 6th centuries, resulting in the early medieval territories of Alemannia (Swabia) and Upper Burgundy. The Helvetii were largely assimilated by their new rulers, contributing to the ethnogenesis of modern Swiss people.

The Belgae (/ˈbɛldʒiː/ BELL-jee, /-ɡaɪ/ -⁠gye) were a large confederation of tribes living in northern Gaul, between the English Channel, the west bank of the Rhine, and the northern bank of the river Seine, from at least the third century BC. They were discussed in depth by Julius Caesar in his account of his wars in Gaul. Some peoples in southern Britain were also called Belgae and had apparently moved from the continent. T. F. O'Rahilly believed that some had moved further west and he equated them with the Fir Bolg in Ireland. The Roman province of Gallia Belgica was named after the continental Belgae. The term continued to be used in the region until the present day and is reflected in the name of the modern country of Belgium.

The Britons (*Pritanī, Latin: Britanni, Welsh: Brythoniaid), also known as Celtic Britons or ancient Britons, were the Celtic people who inhabited Great Britain from at least the British Iron Age until the High Middle Ages, at which point they diverged into the Welsh, Cornish, and Bretons (among others). They spoke Common Brittonic, the ancestor of the modern Brittonic languages.

The earliest written evidence for the Britons is from Greco-Roman writers and dates to the Iron Age. Ancient Britain was made up of many tribes and kingdoms, associated with various hillforts. The Britons followed an ancient Celtic religion overseen by druids. Some of the southern tribes had strong links with mainland Europe, especially Gaul and Belgica, and minted their own coins. The Roman Empire conquered most of Britain in the 1st century AD, creating the province of Britannia. The Romans invaded northern Britain, but the Britonnic tribes such as the Caledonians and Picts in the north remained unconquered, and Hadrian's Wall (which bisects the modern English counties of Northumberland and Cumbria) became the edge of the empire. A Romano-British culture emerged, mainly in the southeast, and British Latin coexisted with Brittonic. It is unclear what relationship the Britons had with the Picts, who lived outside of the empire in northern Britain; however, most scholars today accept the fact that the Pictish language was closely related to Common Brittonic.