Ionian Greeks, originating from Phocaea, establish the colony of Massalia (present-day Marseille), on the shores of the Mediterranean Sea, in 600 BCE.

This makes it France's oldest city.

At the same time, some Gallic Celtic tribes penetrate parts of the current territory of France, and this occupation spreads to the rest of France between the fifth and third centuries BCE.

The concept of Gaul emerges at this time; it corresponds to the territories of Celtic settlement ranging between the Rhine, the Atlantic Ocean, the Pyrenees and the Mediterranean.

The borders of modern France are roughly the same as those of ancient Gaul, which is inhabited by Celtic Gauls.

Gaul is at this time a prosperous country, of which the southernmost part is heavily subject to Greek and Roman cultural and economic influences.

Around 390 BCE the Gallic chieftain Brennus and his troops make their way to Italy through the Alps, defeat the Romans in the Battle of the Allia, and besiege and ransom Rome.

The Gallic invasion leaves Rome weakened, and the Gauls continue to harass the region until 345 BCE when they enter into a formal peace treaty with Rome, but the Romans and the Gauls will remain adversaries for the next several centuries, and the Gauls will continue to be a threat in Italia.

The Senones, a Gallic tribe originating from the modern areas of France known as Seine-et-Marne, Loiret, and Yonne, have expanded to occupy northern Italy, making their way over the Alps in about 400 BCE and, having driven out the Umbrians, settling on the east coast of Italy from Ariminum to Ancona, in the so-called ager Gallicus, and establish the town of Sena Gallica (Sinigaglia), which becomes their capital.

Etruscan territory has shrunk as a direct result of challenges by the Latin League in central Italy.

Celtic tribes (“Gauls” according to Roman historian Levy and others); called Senones by Polybius), under King Brennus, had crossed the Alps in about 400, and shatter the Etruscan defenses at Clusium (Chiusi) in 391.

A call for aid brings a Roman peace delegation that attempts, vainly, to persuade the Gauls to return north, apparently offering a diplomatic insult in the process.

Refusing, …

Part of the Gallic tribe of the Senones had in about 400 BCE had made their way over the Alps and settled on the east coast of Italy from Ariminum to Ancona, in the so-called ager Gallicus, and founded the town of Sena Gallica (Sinigaglia), which has become their capital.

They had invaded Etruria and besieged Clusium in 391 BCE.

The Clusines had appealed to Rome, whose intervention, accompanied by a violation of the law of nations, had led to war, the defeat of the Romans at the Allia (July 18, 390 BCE) and the capture of Rome.

The Senones have been engaged in hostilities with the Romans for decades, but in 331 BCE conclude a peace with Rome and enter upon a period of friendly relations which is to last the rest of the century.

The Romans establish the town of Pisaurum as a colony in the territory of the Piceni, a tribe living in the Marche on the Adriatic.

The northern Piceni had been invaded in the fourth century BCE by the Senones Gauls, and when the Romans reached the area the population was a mix of the two races.

Within it the Gauls at least were still distinct, as the Romans separated them out and expelled them from the country.

The Parisii and the Roman Conquest of the Paris Basin (52 BCE)

The Parisii, a sub-tribe of the Celtic Senones, inhabited the Paris basin near the Seine River from around 250 BCE. Their chief settlement, an oppidum called Lutetia (modern Paris), was a key trade and strategic center in northern Gaul.

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The Parisii in the Gallic Revolt Against Rome (52 BCE)

• The Parisii allied with the Suessiones in support of Vercingetorix’s rebellion against Julius Caesar.
• They participated in the pan-Gallic uprising, resisting Roman expansion into central and northern Gaul.
• Their forces fought alongside other Gallic tribes at Alesia, where Vercingetorix was ultimately defeated.

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The Roman Conquest of the Paris Basin

• After the Battle of Alesia (52 BCE) and the collapse of the Gallic coalition, Roman legions moved into the Parisii homeland.
• The Parisii, like other rebellious tribes, were subdued, and Roman rule was firmly established in the region.
• The Romans fortified Lutetia, eventually transforming it into an important Romanized settlement under Gallia Lugdunensis.

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Legacy and Transformation Under Rome

• Lutetia (Lutece) became a key Gallo-Roman city, benefiting from trade, roads, and Roman infrastructure.
• The region gradually assimilated Roman culture, with the Latin language, Roman laws, and urbanization shaping its development.
• Over the centuries, Lutetia would grow into the medieval and modern city of Paris, preserving its ancient Gallic roots within its evolving Roman identity.

The fall of the Parisii and the conquest of the Paris basin marked a crucial step in Rome’s consolidation of Gaul, solidifying its control over northern France and laying the foundation for centuries of Roman influence in the region.