Gallia Cisalpina in the context of "Battle of Vercellae"

Gaul (Latin: Gallia) was a region of Western Europe first clearly described by the Romans, encompassing present-day France, Belgium, Luxembourg, and parts of Switzerland, the Netherlands, Germany, and Northern Italy. It covered an area of 494,000 km (191,000 sq mi). According to Julius Caesar, who took control of the region on behalf of the Roman Republic, Gaul was divided into three parts: Gallia Celtica, Belgica, and Aquitania. Archaeologically, the Gauls were bearers of the La Tène culture during the 5th to 1st centuries BC. This material culture was found throughout Gaul and as far east as modern-day southern Poland, Slovakia, and Hungary.

Warbands led by the Gaul Brennos sacked Rome in 387 BC, becoming the only time Rome was conquered by a foreign enemy in 800 years. However, Gallia Cisalpina was conquered by the Romans in 204 BC and Gallia Narbonensis in 123 BC. Gaul was invaded after 120 BC by the Cimbri and the Teutons, who were in turn defeated by the Romans by 103 BC. Julius Caesar finally subdued the largest part of Gaul in his campaigns from 58 to 51 BC. Roman control of Gaul lasted for five centuries, until the last Roman rump state, the Domain of Soissons, fell to the Franks in AD 486.

The murmillo (also sometimes spelled "mirmillo", "myrmillo", or "mirmillones" pl. murmillones) was a type of gladiator during the Roman Imperial age. The murmillo-class gladiator developed in the early Imperial period to replace the earlier Gallus-type gladiator, named after the warriors of Gaul (Latin: Gallus, lit. 'a Gaul'). As the Gauls inhabiting Italy had become well integrated with the Romans by the time of the reign (27 BCE to 14 CE) of Augustus, it became undesirable to portray them as enemy outsiders; the Gallus-class gladiator thus fell out of use.

The designation murmillo originated with the Greek word μορμύρος (mormyrus) for a type of fish - murmillo gladiators could wear a Gallic-model helmet incorporating fish-imagery.