/ Gallic warrior © Vincent FlachaireTo protect its commercial interests and coastal settlements, Massalia sought Rome's help in conflicts with some Celto-Ligurian peoples. These interventions allowed the Romans gradually to strengthen their presence in the region.
Roman interventions increased during the second century BC. Sextius Calvinus captured Entremont in 123 BC, although occupation continued after this first destruction. Aquae Sextiae, modern Aix-en-Provence, was founded in 122 BC. The conquest secured a land route between Italy and Spain across Transalpine Gaul. Narbonne became a Roman colony in 118 BC; the province would later be known as Gallia Narbonensis.
In the late second century BC, the movements of the Cimbri and Teutones threatened Roman-controlled territories. In 105 BC, Roman armies suffered a major defeat at Arausio, modern Orange. In 102 BC, Marius defeated the Teutones and Ambrones near Aquae Sextiae.
From 58 BC, Julius Caesar led the conquest of Gaul. During his civil war against Pompey, Marseille supported the Pompeian side. Besieged and defeated in 49 BC, the city lost much of its territory and political autonomy.
Sources and further reading: French Ministry of Culture: the end of Entremont; City of Aix-en-Provence: twenty centuries of urban history.