Caesar's Invasions of Britain (55-54 BC): Rome Crosses the Sea

Julius Caesar’s invasions of Britain were two military expeditions across the English Channel in 55 and 54 BC, launched during his conquest of Gaul. They were the first Roman armies to set foot on the island. Caesar won battles against the Britons and their war leader Cassivellaunus, but storms, supply problems and unrest in Gaul kept him from staying, and Britain remained outside the Roman Empire for almost another century.

Background: an island at the edge of the world

To most Romans, Britain was a land of legend beyond the Ocean, known mainly through traders and the voyage of the Greek explorer Pytheas in the fourth century BC. The south-east, however, was closely linked to northern Gaul by trade, language and politics; some British and Belgic Gaulish peoples shared names and rulers.

By 55 BC Caesar had spent three years fighting in Caesar’s Gallic Wars. He justified a crossing on the grounds that Britons had sent help to his Gallic enemies. Crossing the Ocean also promised enormous prestige in Rome, where his political position depended on spectacular success, and a chance to learn what the island held.

The first expedition, 55 BC

Late in the campaigning season, Caesar sent an officer, Gaius Volusenus, to scout the coast in a warship and dispatched Commius, a king of the Gallic Atrebates whom he trusted, to win over British peoples. The Britons arrested Commius on arrival.

Caesar sailed from the territory of the Morini, probably near Boulogne, with two legions, the Seventh and the Tenth, in about 80 transport ships. His cavalry, in a separate group of 18 ships, failed to reach Britain. Finding British warriors massed on the cliffs at Dover, he moved along the coast and landed on an open beach, traditionally placed near Deal or Walmer in Kent.

The landing was contested. Heavily laden soldiers hesitated to jump into deep water until, as Caesar tells it, the eagle-bearer of the Tenth Legion leapt into the sea and called on his comrades to follow rather than abandon the standard. The Romans forced their way ashore and the Britons asked for peace.

Days later a storm coinciding with a high spring tide wrecked or damaged many of the ships drawn up on the beach. The Britons renewed the fight, attacking a legion out foraging with war chariots, a style of fighting Caesar describes with evident interest. After repairing what ships he could and winning another engagement, Caesar returned to Gaul before the autumn equinox, having spent about three weeks in Britain. In Rome the Senate nonetheless voted 20 days of public thanksgiving, an unprecedented honour.

The second expedition, 54 BC

Caesar prepared much more carefully for 54 BC. He had new ships built, lower and broader for beaching, and sailed in early July with five legions and about 2,000 cavalry. Counting private vessels, he reports more than 800 ships, a fleet that frightened the Britons away from the beach. The landing was unopposed; excavations published by the University of Leicester in 2017 identified a large defended camp of this period at Ebbsfleet on Pegwell Bay in Kent, which may mark the landing area.

Caesar pushed inland and took a fortified site, often identified with Bigbury hillfort near Canterbury. Then another storm wrecked about 40 ships, forcing him to return to the coast for ten days to repair the fleet and fortify a naval camp.

Meanwhile the Britons had united under Cassivellaunus, a ruler whose lands lay north of the Thames. Rather than risk a pitched battle, Cassivellaunus used his chariots to harass Roman columns and foragers. Caesar forced a crossing of the Thames, probably somewhere west of London, despite stakes planted in the riverbed.

Cassivellaunus’s coalition then began to break apart. The Trinovantes of Essex, whose young prince Mandubracius had fled to Caesar after his father was killed by Cassivellaunus, submitted and supplied grain, and several other peoples followed. Caesar captured Cassivellaunus’s stronghold, possibly near Wheathampstead in Hertfordshire, while an attack by four Kentish kings on the Roman naval camp failed.

Cassivellaunus negotiated through Commius. Caesar demanded hostages, fixed an annual tribute to be paid to Rome and ordered that the Trinovantes be left alone. With unrest growing in Gaul and the season late, he took his army back across the Channel in September.

Key people

• Julius Caesar (100-44 BC): Roman governor of Gaul, who led both expeditions in person and wrote the only detailed account of them in Books 4 and 5 of his Commentaries.
• Cassivellaunus: British war leader from north of the Thames, chosen to command the allied peoples in 54 BC. He is the first named Briton in recorded history.
• Commius: King of the Atrebates in Gaul, installed by Caesar, who acted as his envoy to the Britons and later joined the Gallic revolt of 52 BC against him.
• Mandubracius: Prince of the Trinovantes who sought Caesar’s protection; his restoration was one of the conditions of peace.
• Gaius Volusenus: Roman officer who scouted the British coast before the first crossing.
• Quintus Tullius Cicero: Brother of the orator and one of Caesar’s legates in 54 BC, whose reports home are echoed in his brother’s surviving letters, a small independent source.

What did Caesar achieve?

Militarily, Caesar showed that Roman armies could cross the Ocean and defeat the Britons, but he gained no territory and left no garrison. It is unclear whether the tribute was ever paid for long. Cicero, whose brother Quintus served on the expedition, wrote in a letter that there was no silver in the island and no hope of plunder except slaves.

The political effect in Rome was larger. Crossing the Ocean to a near-mythical land enhanced Caesar’s fame at a time when his rivals were seeking to limit him. His Commentaries also gave Romans their first detailed account of Britain, including descriptions of British chariot warfare and the famous note that Britons dyed themselves with woad to look more terrifying in battle.

Legacy

The expeditions created lasting diplomatic ties. Over the next century, rulers in south-east Britain traded intensively with the Roman world, imported wine and luxury goods, and some styled themselves on their coins as Roman allies. Commius himself later turned against Caesar and is thought to have ended his life in Britain, where coins of rulers claiming descent from him appear.

Later Romans remembered Caesar’s campaigns as unfinished business. Augustus considered an invasion but never carried it out, and Caligula assembled an army on the Channel coast in AD 40 without crossing. The emperor Claudius finally ordered the Roman conquest of Britain in AD 43, beginning nearly four centuries of Roman rule that lasted until the end of Roman Britain in the early fifth century.

Timeline

• 55 BC, summer: Volusenus scouts the British coast; Commius is sent ahead and arrested.
• 55 BC, late August: Caesar lands in Kent with two legions after an opposed landing.
• 55 BC, about September: A storm wrecks ships; Caesar returns to Gaul after roughly three weeks.
• 54 BC, early July: Caesar crosses with five legions and about 2,000 cavalry and lands unopposed.
• 54 BC, July-August: A storm damages the fleet; Caesar crosses the Thames and defeats Cassivellaunus.
• 54 BC, September: Peace terms are agreed and the army returns to Gaul.
• AD 43: The Roman conquest of Britain begins under Claudius.

Why it matters

Caesar’s expeditions brought Britain into the written history and political orbit of Rome for the first time. They did not conquer the island, but they established contacts, knowledge and ambitions that led directly to the Roman conquest a century later, which shaped Britain’s towns, roads and history for four hundred years.