Gaul (Gallia) was the Roman name for the region of Western Europe comprising present day northern Italy, France, Belgium, western Switzerland and the parts of the Netherlands and Germany on the west bank of the River Rhine. In English, the word Gaul (Gaulois) may also refer to an inhabitant of that region, although the expression may be used more generally for all ancient speakers of the Gaulish language (a derivative of early Celtic) who were widespread in Europe and extended even into central Anatolia by Roman times.
Gauls under Brennus sacked Rome circa 390 BC. In the Aegean world, a huge migration of Eastern Gauls appeared in Thrace, north of Greece, in 281 BC. Another Gaulish chieftain also named Brennus, at the head of a large army, was only turned back from desecrating the Temple of Apollo at Delphi in Greece at the last minute — he was alarmed, it was said, by portents of thunder and lightning. At the same time a migrating band of Celts, some 10,000 warriors, with their women and children and slaves, were moving through Thrace. Three tribes of Gauls crossed over from Thrace to Asia Minor at the express invitation of Nicomedes I, king of Bithynia (which was a small geographical location just south of the Bosphorus and the Euxine (Black Sea) in the northern area of modern-day Turkey, i.e just south and southeast of the latter-day city of Constantinople, or modern-day Istanbul), who required help in a dynastic struggle against his brother. Eventually they settled down in eastern Phrygia and Cappadocia in central Anatolia, a region henceforth known as Galatia.
The names Gallia and Galatia sometimes are compared to Gael, which is, however, from Goidhel or Gwyddel, and cannot be directly related, though it should be noted the term Goidhel is derived from the Old Welsh Guoidel meaning "pirate, raider". It is uncertain whether the Gal- names are from a native name of a tribe, or if they are exonyms. Birkhan (1997) considers a root * g(h)al- "powerful" (PIE * gelh, well-attested in Celtic, and with cognates in Balto-Slavic), but speculates that the name also could be taken from a Gallos River, comparable to the names of the Volcae and the Sequani which are likely derived from hydronyms. There also have been attempts to trace Keltoi and Galatai to a single origin. It is most likely that the terms originated as names of minor tribes * Kel-to and/or Gal(a)-to- which were the earliest to come into contact with the Roman world, but which have disappeared without leaving a historical record.
In English usage the words Gaul and Gaulish are used synonymously with Latin Gallia, Gallus and Gallicus. However the similarity of the names is probably accidental: the English words are borrowed from French Gaule and Gaulois, which appear to have been borrowed themselves from Germanic walha-, the usual word for the non-Germanic-speaking peoples (Celtic-speaking and Latin-speaking indiscriminately). Germanic w is regularly rendered with French gu / g (cf. guerre = war, garder = ward), and the diphthong au is the regular outcome of al before a following consonant (cf. cheval ~ chevaux). Gaule or Gaulle can hardly be derived from Latin Gallia, since g would become j before a (cf. gamba > jambe), and the diphthong au would be incomprehensible; the regular outcome of Latin Gallia would have been * Jaille in French.
Hellenistic aitiology connects the name with Galatia (first attested by Timaeus of Tauromenion in the 4th c. BC), and it was suggested that the association was inspired by the "milk-white" skin (γάλα, gala, "milk") of the Gauls (Greek: Γαλάται, Galatai, Galatae).
The early history of the Gauls is predominantly a work in archaeology — there being little written information (save perhaps what can be gleaned from coins) concerning the peoples that inhabited these regions — and the relationships between their material culture, genetic relationships (the study of which has been aided, in recent years, through the field of archaeogenetics), and linguistic divisions rarely coincide.
The major source of materials on the Celts of Gaul was Poseidonios of Apamea, whose writings were quoted by Timagenes, Julius Caesar, the Sicilian Greek Diodorus Siculus, and the Greek geographer Strabo.
Many cultural traits of the early Celts seem to have been carried northwest up the Danube Valley, although this issue is contested. It seems as if they derived many of their skills (like metal-working), as well as certain facets of their culture, from Balkan peoples. Some scholars think that the Bronze Age Urnfield culture represents an origin for the Celts as a distinct cultural branch of the Indo-European-speaking peoples (see Proto-Celtic). The Urnfield culture was preeminent in central Europe during the late Bronze Age, from ca. 1200 BC until 700 BC. The spread of iron-working led to the development of the Hallstatt culture (ca. 700 to 500 BC) directly from the Urnfield. Proto-Celtic, the latest common ancestor of all known Celtic languages, is considered by some scholars to have been spoken at the time of the late Urnfield or early Hallstatt cultures.
The Hallstatt culture was succeeded by the La Tène culture, which developed out of the Hallstatt culture without any definite cultural break, under the impetus of considerable Mediterranean influence from the Greek, and Etruscan civilisations. The La Tène culture developed and flourished during the late Iron Age (from 450 BC to the Roman conquest in the 1st century BC) in France, Switzerland, Austria, southwest Germany, Bohemia, Moravia, Slovakia and Hungary. Farther north extended the contemporary Pre-Roman Iron Age culture of northern Germany and Scandinavia.
By the second century BC, France was called Gaul (Gallia Transalpina) by the Romans. In his Gallic Wars, Julius Caesar distinguishes among three ethnic groups in Gaul: the Belgae in the north (in what is present-day Belgium), the Celts in the centre, and the Aquitani in the southwest. While some scholars believe that the Belgae were a mixture of Celtic and Germanic elements, their ethnic affiliations have not been definitively resolved. One of the reasons is political interference upon the French historical interpretation during the 19th century. French historians adopted fully the explanation of Caesar who stated that Gaul stretched from the Pyrenees up to the Rhine in the north. This fitted the French expansionist aspirations of the time under Napoleon III of France. But Caesar wrote: "The Aquitani can give the Romans lessons in good Latin." In the north of (modern) France, the Gaul-German language border was situated somewhere next to the River Somme. Northern Belgic tribes like the Nervians, Atrebates or Morini were without doubt Germanic languages speakers. In addition to the Gauls, there were other peoples living in Gaul, such as the Greeks and Phoenicians who had established outposts such as Massilia (present-day Marseille) along the Mediterranean coast. Also, along the southeastern Mediterranean coast, the Ligures had merged with the Celts to form a Celto-Ligurian culture.
In the second century BC, Mediterranean Gaul had an extensive urban fabric and was prosperous, while the heavily forested northern Gaul had almost no cities outside of fortified compounds (or oppida) used in times of war. The prosperity of Mediterranean Gaul encouraged Rome to respond to pleas for assistance from the inhabitants of Massilia, who were under attack by a coalition of Ligures and Gauls. The Romans intervened in Gaul in 125 BC, and by 121 BC they had conquered the Mediterranean region called Provincia (later named Gallia Narbonensis). This conquest upset the ascendancy of the Gaulish Arverni tribe.
As many as a million people (probably 1 in 4 of the Gauls) died, another million were enslaved, 300 tribes were subjugated and 800 cities were destroyed during the Gallic Wars. The entire population of the city of Avaricum (Bourges) (40,000 in all) were slaughtered. During Julius Caesar's campaign against the Helvetii (present-day Switzerland) approximately 60% of the tribe was destroyed, and another 20% was taken into slavery.
From the 3rd to 5th centuries, Gaul was exposed to raids by the Franks. The Gallic Empire broke away from Rome from 260 to 273, consisting of the provinces of Gaul, Britannia, and Hispania, including the peaceful Baetica in the south. Following the Frankish victory at the Battle of Soissons in AD 486, Gaul (except for Septimania) came under the rule of the Merovingians, the first kings of France.
Gallo-Roman culture, the Romanized culture of Gaul under the rule of the Roman Empire, persisted particularly in the areas of Gallia Narbonensis that developed into Occitania, Gallia Cisalpina and to a lesser degree, Aquitania. The formerly Romanized north of Gaul, once it had been occupied by the Franks, would develop into Merovingian culture instead. Roman life, centered on the public events and cultural responsibilities of urban life in the res publica and the sometimes luxurious life of the self-sufficient rural villa system, took longer to collapse in the Gallo-Roman regions, where the Visigoths largely inherited the status quo in the early 5th century. Gallo-Roman language persisted in the northeast into the Silva Carbonaria that formed an effective cultural barrier with the Franks to the north and east, and in the northwest to the lower valley of the Loire, where Gallo-Roman culture interfaced with Frankish culture in a city like Tours and in the person of that Gallo-Roman bishop confronted with Merovingian royals, Gregory of Tours.
The Druids were not the only political force in Gaul, however, and the early political system was complex, if was ultimately fatal to the society as a whole. The fundamental unit of Gallic politics was the tribe, which itself consisted of one or more of what Caesar called "pagi." Each tribe had a council of elders, and initially a king. Later, the executive was an annually-elected magistrate. Among the Aedui, a tribe of Gaul, the executive held the title of "Vergobret," a position much like a king, but its powers were held in check by rules laid down by the council.
The tribal groups, or pagi as the Romans called them (singular: pagus; the French word pays, "region", comes from this term) were organised into larger super-tribal groups that the Romans called civitates. These administrative groupings would be taken over by the Romans in their system of local control, and these civitates would also be the basis of France's eventual division into ecclesiastical bishoprics and dioceses, which would remain in place — with slight changes — until the French Revolution.
Although the tribes were moderately stable political entities, Gaul as a whole tended to be politically-divided, there being virtually no unity among the various tribes. Only during particularly trying times, such as the invasion of Caesar, could the Gauls unite under a single leader like Vercingetorix. Even then, however, the faction lines were clear.
The Romans divided Gaul broadly into Provincia (the conquered area around the Mediterranean), and the northern Gallia Comata ("free Gaul" or "long haired Gaul"). Caesar divided the people of Gaulia Comata into three broad groups: the Aquitani; Galli (who in their own language were called Celtae); and Belgae. In the modern sense, Gaulish tribes are defined linguistically, as speakers of dialects of the Gaulish language. While the Aquitani were probably Vascons, the Belgae would thus probably be counted among the Gaulish tribes, perhaps with Germanic elements.
The Gauls practiced a form of animism, ascribing human characteristics to lakes, streams, mountains, and other natural features and granting them a quasi-divine status. Also, worship of animals was not uncommon; the animal most sacred to the Gauls was the boar, which can be found on many Gallic military standards, much like the Roman eagle.
Their system of gods and goddesses was loose, there being certain deities which virtually every Gallic person worshiped, as well as tribal and household gods. Many of the major gods were related to Greek gods; the primary god worshiped at the time of the arrival of Caesar was Teutates, the Gallic equivalent of Mercury. The "father god" in Gallic worship was "Dis Pater," who could be assigned the Roman name "Saturn." However there was no real theology, just a set of related and evolving traditions of worship.
Perhaps the most intriguing facet of Gallic religion is the practice of the Druids. There is no certainty concerning their origin, but it is clear that they vehemently guarded the secrets of their order and held sway over the people of Gaul. Indeed they claimed the right to determine questions of war and peace, and thereby held an "international" status. In addition, the Druids monitored the religion of ordinary Gauls and were in charge of educating the aristocracy. They also practiced a form of excommunication from the assembly of worshippers, which in ancient Gaul meant a separation from secular society as well. Thus the Druids were an important part of Gallic society.