Gallia Belgica (Belgic Gaul) was a province of the Roman empire located in what is now northern France, Belgium, Luxembourg, the southern part of the Netherlands, and the German Rhineland. It was originally composed of the lands of the alliance of the Belgae who had fought against Julius Caesar, plus the lands of the Treveri, Mediomatrici and Leuci. Its southern border with Celtic Gaul and the Belgae was the original cultural boundary reported by Caesar and formed by the Marne and Seine rivers.
The province was decreased in size over time. It must have originally bordered upon the Rhine, which is how Pliny the Elder describes it, but this area was colonized by Roman colonies and in-coming German tribes from east of the Rhine, which quickly developed their own administration. Much later, the territory was reduced when the emperor Diocletian, split the northeastern territory of the Tungri into Germania Inferior, joining the Rhineland colonies, and the remaining part of Gallia Belgica was split into Belgica Prima in the eastern area of the Treveri, Mediomatrici and Leuci, around Luxembourg and the Ardennes, and Belgica Secunda between the English channel and the River Meuse, which therefore contained the original "Belgium" that Caesar had described. The capital of Belgica Prima, Trier, became an important late Roman capital.
Roman conquest 
In 57 BC, Julius Caesar led the conquest of northern Gaul, and already specified that the part to the north of the Seine and Marne rivers was inhabited by a people or alliance known as the Belgae. This definition became the basis of the later Roman province of Gallia Belgica. Caesar said that the Belgae were separated from the Celtic Gauls to their south by "language, custom and laws" (lingua, institutis, legibus) but he did not go into detail, except to mention that he learnt from his contacts that the Belgae had some ancestry from east of the Rhine, which he referred to as Germania. Some of the Belgic tribes closest to the Rhine he described as the Germani cisrhenani. Modern historians interpret Caesar and the archaeological evidence as indicating that the core of the Belgic alliance was in northern France, the Suessiones, Viromandui and Ambiani and perhaps some of their neighbours, who live in the area Caesar identifies as "Belgium". These were the leaders of the initial military alliance he confronted, and they were also more economically advanced (and therefore less "Germanic" according to Caesar's way of seeing things) than many of their more northerly allies such as the Germani Cisrhenani.
Save the southern Remi, all the tribes allied against the Romans, fearful of isolation if the rest of the region was conquered and angry at the Roman decision to garrison legions in their territory the preceding winter. Contemporary estimates of the allies' combined strength numbered the troops at 288,000, led by the Suessione king, Galba. Due to the Belgic coalition's size and reputation for uncommon bravery, Caesar avoided meeting the combined forces of the tribes in battle. Instead, he used cavalry to skirmish with smaller contingents of tribesmen. Only when Caesar managed to isolate one of the tribes did he risk conventional battle. The tribes fell in a piecemeal fashion and Caesar claimed to offer lenient terms to the defeated, including Roman protection from the threat of surrounding tribes. Most tribes agreed to the conditions. A series of uprisings followed the 57 BC conquest. The largest revolt was led by the Bellovaci in 52 BC, after the defeat of Vercingetorix. During this rebellion, it was the Belgae who avoided direct conflict. They harassed the Roman legions, led personally by Caesar, with cavalry detachments and archers. The rebellion was put down after a Bellovaci ambush of the Romans failed. The revolting party was slaughtered.
Formation of Gallia Belgica 
The province of Gallia Belgica was originally part of Gallia Comata. However, this governmental structure proved ineffective. Following a census of the region in 27 BC, Augustus ordered a restructuring of the provinces in Gaul. Therefore in 22 BC, Marcus Agrippa split Gallia Comata into three regions (Gallia Aquitania, Gallia Lugdunensis and Gallia Belgica.) Agrippa made the divisions on what he perceived to be distinctions in language, race and community - Gallia Belgica was meant to be a mix of Celtic and Germanic peoples. The capital of this territory was Reims, according to the geographer Strabo, though later the capital moved to modern day Trier. The date of this move is uncertain.
Modern historians view the term 'Gaul' and its subdivisions as a "product of faulty ethnography" and see the split of Gallia Comata into three provinces as an attempt to construct a more efficient government, as opposed to a cultural division. Successive Roman emperors struck a balance between Romanizing the people of Gallia Belgica and allowing pre-existing culture to survive. The Romans allowed local governments to survive, typically in the form of Cantons, however their number in Gallia Belgica was curbed. Roman government was run by Concilia in Reims or Trier. Additionally, local notables from Gallia Belgica were required to participate in a festival in Lugdunum (modern Lyon) which typically celebrated or worshiped the emperor’s genius. The gradual adoption of Romanized names by local elites and the Romanization of laws under local authority demonstrate the effectiveness of this concilium Galliarum. With that said, the concept and community of Gallia Belgica did not predate the Roman province, but developed from it.
Under the Emperors 
During the 1st century AD (estimated date 90 AD), the provinces of Gaul were restructured. Emperor Domitian reorganized the provinces in order to separate the militarized zones of the Rhine from the civilian populations of the region. The northeastern part of Gallia Belgica was split off and renamed Germania Inferior, later to be reorganized and renamed as Germania Secunda. This included the eastern part of modern Belgium, the southernmost part of the modern Netherlands, and a part of modern Germany. The eastern part was split off to become Germania Superior (parts of western Germany and eastern France) and the southern border of Gallia Belgica was extended to the south. The newer Gallia Belgica included the cities of Camaracum (Cambrai), Nemetacum (Arras), Samarobriua (Amiens), Durocorter (Reims), Diuidorum (Metz) and Augusta Treverorum (Trier).
Emperor Diocletian restructured the provinces around 300, and split Belgica into two provinces: Belgica Prima and Belgica Secunda. Belgica Prima had Treveri (Trier) as its main city, and consisted of the eastern part. The border between Belgica Prima and Belgica Secunda was approximately along the River Meuse.
Fall of Gallia Belgica 
In 406 AD, the Vandals, Burgundians and other tribes crossed the Rhine and defeated the Gaulish forces. The Franks had already infiltrated Germania Inferior and controlled it since at least 350 AD. They emerged victorious and Belgica Secunda became in the 5th century the center of Clovis' Merovingian kingdom and during the 8th century the heart of the Carolingian Empire. After the death of Charlemagne's son, Louis the Pious, the region was divided by the Treaty of Verdun in 843. The three sons of Louis the Pious divided his territories into three kingdoms: East Francia, West Francia which became the kernel of modern France, and Middle Francia which was succeeded by Lotharingia. Though often presented as the dissolution of the Frankish empire, it was in fact the continued adherence to Salic patrimony. Lotharingia was divided in 870 by the Treaty of Meerssen under West and East Francia.
Belgica as the name of the Low Countries 
Although the name "Belgica" is now reserved for Belgium, before the division of the Low Countries into a southern and a northern half in the 16th century, the name referred to the entire Low Countries. The Seventeen Provinces of the Low Countries were then divided into the independent Belgica Foederata or the federal Dutch Republic and the Belgica Regia or the royal Southern Netherlands under the Habsbourgian crown. For example, several contemporary maps of the Dutch Republic, which consisted of the Northern Netherlands, and therefore has almost no overlap with the country of Belgium, show the Latin title Belgium Foederatum.
See also 
- "Gallos ab Aquitanis Garumna flumen, a Belgis Matrona et Sequana diuidit.", Commentarii de Bello Gallico
- Wightman, Edith Mary (1985), Gallia Belgica, University of California Press page 12-14.
- Gaius Julius Caesar. The Conquest of Gaul. Trans. S.A. Handford (New York: Penguin, 1982), pp. 59-60.
- Gaius Julius Caesar. The Conquest of Gaul. Trans. S. A. Handford (New York: Penguin, 1982); pp. 59, 70, 72.
- Matthew Bunson. Encyclopedia of the Roman Empire (New York: Facts on File, 1994), p. 169.
- The Cambridge Ancient History, New Ed., Vol. 10 (London: Cambridge University Press, 1970), p. 469.
- Edith Mary Wightman, Gallia Belgica (Los Angeles: University of California Press, 1985), pp. 57-62, 71-74.
- Mary T. Boatwright, Daniel J. Gargola and Richard J. A. Talbert. A Brief History of the Romans (New York: Oxford University Press, 2006), p. 224.
- For example, the map "Belgium Foederatum" by Matthaeus Seutter, from 1745, which shows the current Netherlands.