"Galatai", Latin Galatae, Galli, and Gallograeci to referred to the Galatians or the Gauls. A difference must be done with the Celts (From the Greek "Keltoi") which were mixed populations living in actual southern France and in the Rhone valley. They were in contect with Greek civilization from Massilia early on, and traded exensively with the Mediterranean. The "Gauls" proper were rather assimilated to the uncivilized populations tht lived in the rest of the area, and nothern tribes in contact with the Belgians and Germannic tribes.
Gallic raids has been extensive in the Mediterranean: From their original population area in Switzerland, Bohemia, and Austria during the bronze to the iron age, they spread into Europe, colonizing southern and central Germany, actual Hungary and up to Romania (in contact with the Scythian-influenced Getai tribe), Belgium and actual Gaul. Ancient gauls gradually passed from a nomadic or semi-nomadic and pastoralist existence inherited from their indo-European ancestry, to a settled existence and agricultural society. More importantly they launched, perhaps because of their population dynamic, or simply for plundering richer lands, a serie of raids in nearby Italy and the Balkans later.
First great migration in Italy (Vth cent. BC)
Italy took the brunt of these attacks. Gallic tribes forced they way through Alpine passes coming from the west (southern Gaul) but also from the land of Boians in the east and Helvetii and other populations in the north. On their path were rich and fertile lands of the Etruscans. They resisted for a hundred of years but were gradually pushed back and/or assimilated.
They were perhaps the main reason behind the demise and the fall of the Etruscan civilization. Pockets existed however behind the Appenine range, south of the Pô valley, the immense, flat plain that existed between the Alps and these mountain range, natural belt of inner Italy. This plain ended in marshes in the Veneti country. The latter were of partial Celtic stock, very ancient.
The population that took hold in Northern Italy (Cisalpine Gaul) and pushed southwards were basically the Boii in the east, subjugating the Venetii, the Senones, the southmost group of the plain, settling on the northwestern coast of the adriatic, and the Insubres, in the west, most probably from Gaul. It is possible also that the Senone were the largest group and were pushed southwards into Pisaurum at a latter date by the fierce Boii from Central Europe. This happened around 400 BC, at which date Rome was a small backwater, independent since about 200 years; In 380 BC the Etruscan league which previously dwelt in this Pô valley was no longer capable of ruling the peninsula. On the other hand the Latium grew in size but was still in contact with bellicose Italic tribes, Osci and Samnites, and the Greeks in the south.
Second great migration in the Balkans (IIIth cent. BC)
So in around 281 BC, a large Gallic move started the second great migration. This time, Northern Italy was already in their hands, so they pushed further east, through the relatively weak Illyrian tribal territories, from Venetium. It was decribed by ancient authors as a lare war band, but it is likely that chariots with wives, childrens ad the elderly were following behind at a distance. This was a raid but with a "one way ticket" apparently for many as they settled where they landed.
The massive, probably composite army of Gauls known as the Tectosages, Volci, Arecomici (nowadays from the Toulouse region or what is called Languedoc), crossed the alps or followed the southern coast (from the Saluvii country), crossed the Pô Valley (we don't know if there was some hostility locally), and reached the northern Balkans. They crossed the Dalmatian country, the Dardanians, pannonians and Breuci, and settled in these wide plains of Pannonia; From there they pushed southwards, to Greece. Some stayed behind or retired there after the retreat from Delphi: The Scordici are perhaps the best known, but the elegeri, Dindari further south, bordering the Paoenians and Thracians, of the northern Iapodes and Letobici are also known heavily eliticized llyrian peoples.
This massive army was led by "Brennus", a generic chieftain title, probably really named Acicorios; The army apparently split up.
The Balkan campaign, defeat and aftermath
Settling in Asia Minor
The Galatian kingdom was established after a Gallic army crossed the Hellespont to the invitation of Nicomedes, king of bithynia in 280 BC to help him warring against his neighbours. They established themselves in Anatolia, and started settling from a small core of 10,000 fighting men and about the same number of women and children, divided into three tribes, Trocmi, Tolistobogii and Tectosages. Defeated by the Seleucids under Antiochus I, they nevertheless raided Phrygia, and the arrival of new Celtic after immigrants felt strong enough to overrunning Bithynia and supported themselves by plundering neighbouring countries. What we know about ancient Galatian warriors ? They were never really "hellenized", although often displaying Greek gear (like helmets and body armour) by taste. They retained their gallic tactics for which they were famed for, but probably relied more on swords than spears due to their plunder.
Axemen, and some archers, javelineers (youth) and slingers were also part of the mix. Chieftains retained a host of close bodyguards, very well equipped with chainmails and longswords, while the rest of the band comprised unarmoured or lightly armoured spearmen and swordsmen. Cavalry was also present, reserved to the aristocratic elite, mounted prefferably on large, imported Nisean horses. There were also local cappadocian axemen and militias that could have been raised, although reluctantly. In time, local mercenaries went to local gear (like the famous depciction of a masked galatian in seleucid service). Galatian mercenaries acted generally as schock troops.
The Galatian state comprised tribes divided into cantons, each governed by a chief ('tetrarch') with powers limited only in cases of murder, which were tried before a council of 300 cantons notables(twelve cantons) meeting twenty miles southwest of Ancyra, at the Drunemeton "holy place of oak". The local Cappadocians were left in control of the towns and the land, paying tributes to their new overlords, a military aristocracy that lived in fortified farmsteads and their warrior bands.
Reputed warriors, respected by both the Greeks and Romans, were often hired as mercenaries (sometimes fighting on both sides). If some armed bands ravaged the western half of Asia Minor, as allies of local kingdoms (like the Bythinians), they sided eventually with the renegade Seleucid prince Antiochus Hierax. He tried to defeat Attalus from Pergamon but the Hellenized cities rallied under Attalus's banner, inflicting several crushing defeats on the Galatians and Seleucids. In 232 the Galatians were forced to settle permanently in the region later known as "Galatia". The Dying Gaul statue displayed in Pergamon commemorated the event, one of the rare depiction by Greeks of a gaul.
Eventually Galatia's borders were formally recognized and later the Attalids employed their services in several occasions. In the early 2nd century BC, they fought hard with Antiochus the Great over Asia Minor. In 189 BC, Rome sent Gnaeus Manlius Vulso on an expedition against the Galatians and defeated them. The kingdom declined and fell under Pontic influence, before being finally freed by the Mithridatic Wars, siding with Rome. In 64 BC, Galatia became an official client-state of the Roman empire, and three chiefs were now appointed to represent the tribes (Tolistobogii -West, Trocmii -East, Tectosages -Center, Ancyra). But this arrangement fell when one of these tetrarchs, Deiotarus claimed sole authority over Galatian lands, finally recognized by the Romans as "king" of Galatia. He died and the Romans eventually given the power to a Roman general close to Brutus and Cassius, Amyntas. He was deposed and replaced when Augustus took over the region, which became a Roman province, part of the Empire.
The Aedui, Tectosages (and sub-tribes like the Trocmi), Allobroges, and others tribes of the Eastern part of Gaul, were probably those that took part in the great Balkanic invasion of 280 BCE (see above). The Gauls in 280 BC had yet not reached the characteristic mobility of their armies at the time Caesar came in 58 BC. Although they largely count on intimidation and shock with an impressive melee infantry, Gallic armies at that time were more complex, and catw has been at the forefront of this research. A typical Gallic army back then comprised mostly spearmen that fought in close order, shieldwalls which were somewhat even closer than the Greek hoplitic formation due to their narrower shields. The warrior class (Cingetos) takes place in the center-front, together with village chieftains, their retinue, high nobles and their own servants and bodyguards called Ambactes, the Soldurii, Champions, and a wide array of lighter sword-and-javelin or more commonly spear-and-javelin troops, the Gaelaiche and Gaesate on the wings of this elite core, plus slingers, archers and skirmishers open the march. Peasant levies (atectoi), and trained ones (Lugoae) took place on the rearguard, while cavalry and chariots took place on the wings. Famously chariots delivered their noble warrior at high speed for a few slashes on the back of the opposing or in the melee, they were used as fast transportation systems, early APCs... Gallic cavalry was reputed and fought opposing cavalry or dismounted as quick reinforcement if needed. Like some Germanic tribes, the Gauls practiced combined infantry and cavalry tactics to best effect.
Trocmii and Tolistboii.