have been found in 8th-century BCE Hallstatt burials in Marmesse, France. These cuirasses bear some similarity to Greek and Etruscan 'bell cuirasses' produced in the Mediterranean during the Archaic Period (8th to 6th century BCE) and to the 'muscle cuirass' which developed in the 5th century BCE. The 1st-century BCE 'Warrior of Grezan', one of the oldest and best examples of Celtic art depicting a warrior, may depict the figure wearing a breastplate.

La Tene helmets of various shapes and designs appear in graves from the 5th century BCE on. However, Celtic helmets are rare, and it is likely that helmets were not widely used by some tribes. Their scarcity backs up Greek and Roman claims that some Celtic tribes scorned the use of helmets. The only area whereA coalition of Celtic tribes under a high king known as Brennus invaded Italy and sacked Rome in 390 BCE, and another ruler called Brennus helped to lead an invasion of Southeastern Europe with a coalition of tribes which culminated in the invasion of Greece c. 280 BCE. 'Brennus' was probably originally a Celtic title which became corrupted and misinterpreted as a name by Greek and Roman writers. The aggressive migration of the Celts into the Mediterranean led to increasingly intense conflicts with the Hellenistic kingdoms and the Roman Republic.

Map of Celtic Peoples in the Post-Classical Period by Magna Celtae (CC BY-NC-ND)

Greek and Roman authors describing conflicts with Celtic tribes noted the differences in Celtic tactics and equipment. However, these accounts are heavily colored by bias and exaggeration.