The Gauls were an iron age Celtic people that inhabited much of modern day France and Belgium during the Roman period (5th century BC to 5th Century AD). The Gauls never united under a single leader or tribe but were made up of various warlike tribes who often fought each other for land and power. They reached their formidable height of power during the 3rd century BC and even sacked Rome herself in the year 387 BC under the warlord Brennus.
After the defeat of Hannibal and Carthage the Romans gradually pushed the Gauls out of northern Italy and they would eventually be completely subjugated by Julius Caesar after the battle of Alesia in 52 BC following a long hard struggle.
After this, Gaul became a province of the Roman Empire, and the Gauls were culturally assimilated into a Gallo-Roman culture, losing their tribal identities by the end of the 1st century AD.