Insubres in the context of "Gaesatae"

Mediolanum, the ancient city where Milan now stands, was originally an Insubrian city, but afterwards became an important Roman city in Northern Italy.

The city was settled by a Celtic tribe belonging to the Insubres group and belonging to the Golasecca culture under the name Medhelanon around 590 BC, conquered by the Romans in 222 BC, who Latinized the name of the city into Mediolanum, and developed into a key centre of Western Christianity and informal capital of the Western Roman Empire. It declined under the ravages of the Gothic War, its capture by the Lombards in 569, and their decision to make Ticinum the capital of their Kingdom of Italy.

Ticinum (the modern Pavia) was an ancient city of Gallia Transpadana, founded on the banks of the river of the same name (now the Ticino) a little way above its confluence with the Padus (Po).

It was said by Pliny the Elder to have been founded by the Laevi and Marici, two Ligurian tribes, while Ptolemy attributes it to the Insubres.Its importance in Roman times was due to the extension of the Via Aemilia from Ariminum (Rimini) to the Padus (or Po) (187 BC), which it crossed at Placentia (Piacenza) and there forked, one branch going to Mediolanum (Milan) and the other to Ticinum, and thence to Laumellum where it divided once more, one branch going to Vercellae, and thence to Eporedia and Augusta Praetoria; and the other to Valentia, and thence to Augusta Taurinorum (Turin) or to Pollentia.

Over the course of nearly four centuries, the Roman Republic fought a series of wars against various Celtic tribes, whom they collectively described as Galli, or Gauls. Among the principal Gallic peoples described as antagonists by Greek and Roman writers were the Senones, Insubres, Boii, and Gaesatae.

The Romans first came into conflict with Gauls who entered Italy from the north. Some of these settled in the lands immediately south of the Alps, which became known as Cisalpine Gaul: "Gaul this side of the Alps". Gaulish armies, some perhaps fighting as mercenaries in the service of the cities of Magna Graecia, plundered territory in Etruria and Latium during the fourth century, famously sacking Rome circa 390 BC.

Western Lombard is a group of varieties of the Lombard language, a Romance language of the Gallo-Italic subgroup. It is spoken primarily in Italy and Switzerland. Within Italy, it is prevalent in the Lombard provinces of Milan, Monza and Brianza, Varese, Como, Lecco, Sondrio, and parts of Cremona (excluding Crema and its immediate surroundings), Lodi, and Pavia. In Piedmont, it is spoken in the provinces of Novara, Verbano-Cusio-Ossola, the eastern area of the Province of Alessandria (around Tortona), and a small part of Vercelli (Valsesia). In Switzerland, Western Lombard is spoken in the canton of Ticino and part of the canton of Graubünden.

Due to its historical association with the Duchy of Milan, Western Lombard is frequently referred to as Insubric (from Insubria and Insubres) or Milanese. The term Cisabduan ("Cisabduano", literally "on this side of the Adda River") is also used, particularly in linguistic contexts, following the terminology introduced by Clemente Merlo.

Viridomarus (or Britomartus as translations vary; died 222 BC) was a Gallic military leader of the Gaesatae. In 222 BC he was hired by the Insubres who were fighting the Romans. Viridomarus led a mercenary army against a Roman army at the Battle of Clastidium. The Romans won the battle, and in the process, Marcus Claudius Marcellus, the Roman leader, earned the spolia opima by killing Viridomarus in single combat.

The Battle of Clastidium was fought in 222 BC between a Roman army led by the consul Marcus Claudius Marcellus and a Celtic force of the transalpine Gaesatae, called by the cisalpine Insubres. The Gaesatae were led by Viridomarus (Florus) or Britomartus (Plutarch), as the name varies in translation. The Romans won the battle, and in the process, Marcellus earned the spolia opima, one of the highest honors in ancient Rome, by killing the king in single combat. It was also notable as one of the few battles won by the Roman cavalry without any aid by the legions.

Insubria is a historical-geographical region which corresponds to the area inhabited in Classical antiquity by the Insubres; the name can also refer to the Duchy of Milan (1395–1810). For several centuries this name stood for an area stretching approximately between the Adda river in the east and the Sesia river in the west, and between the San Gottardo Pass in the north and the Po river in the south, thus it was a synonym of the Milan region and the surrounding countryside corresponding with Lombardy in modern Italy.