Of the inhabitants, those of Cantium (Kent), an entirely maritime district, are far the most advanced, and the type of civilization here prevalent differs little from that of Gaul—Julius Caesar
Introduction
In 1st Century, Celtic maritime networks were revitalized in the northern Atlantic region as a result of Roman commercial activities in southern Gaul (modern day France). Celtic social ties on both sides of the British channel were strengthened and new alliances were formed.
When Julius Caesar marched into free Gaul in 58 BC, these maritime networks were disrupted as he conquered Gaul and put the region under Roman control. His forays into Britain in 55-54 BC introduced the Britons to the reality of Roman power and the consequences of sending their warriors to aid fellow Celts in Gaul.

Roman Eagle Standard
Caesar wrote, ‘no one goes there [Britain] except traders, and even they are acquainted only with the sea-coasts and the areas that are opposite of Gaul.’ Prior to his first excursion in 55 BC, Caesar summoned ‘traders from these parts’ for information of Britain, but they told him nothing of value. This would seem surprising given the extensive trade between Gaul and Britain. A likely explanation is these traders chose to be highly selective with the intelligence they shared. The Gallic traders warned the Britons of Caesar’s intention to land on their island. As a result, several of the British tribes send envoys offering hostages and allegiance to Caesar while he was in Gaul.

Celtic Chariot Comparison to Roman Chariot
Commius, King of the Atrebates
Caesar pursued the offers made by British envoys by sending Commius—a chief of the Atrebates in Gaul and confidant of the Romans—to persuade the Britons not to resist the Romans when they landed in 55 BC. However, Commius was immediately imprisoned by the Britons. He was later handed back as part of of Caesar’s peace settlement with the Celtic leaders on his first expedition. During Caesar’s second expedition to Britain in 54 BC, Commius negotiated the surrender of the British leader Cassivellaunus (see below). Commius remained loyal to Caesar through the Gaulish revolts of 54 BC, and Rome rewarded him by allowing the Atrebates tribe to remain independent and to be exempt from tax.

Diplomatic Gift to a Chieftain ruling in Southern Britain, possibly Commius of the Atrebates.
Although Commius was at first an ally of Rome, he switched sides to join the revolt in Gaul led by Vercingetorix in 52 BC. He later escaped to Britain to join his people who had already settled there. He established a powerful kingdom based at Calleva (modern day Silchester). By about 30 BC, Commius had established himself as king of the Atrebates in Britain and was issuing coins.

Statue of Vercingetorix
Lessons Learned Caesar’s First Expedition
Caesar’s first expedition to Britannia had limited success. The main lesson learned was the ocean and its massive tides and racing currents was a more formidable opponent than the Britons. Natural forces wreaked havoc on the Roman logistics and destroyed several ships. Even though the native Britons were fierce fighters, they were totally unused to facing the disciplined Roman army. The various tribes were politically fragmented and made Roman diplomacy to divide them an effective weapon.

Dover Cliffs Near Julius Caesar’s Landing in Ancient Britain
Mandubracius, King of the Trinovantes
To take advantage of the fragmentation between the tribal kings, Caesar negotiated a deal with Mandubracius, the son of the king of the Trinovantes. He had fled to Gaul to put himself under Caesar’s protection after his father had been killed in a conflict with his neighbor—Cassivellaunus, the king of the Catuvellauni. According to Caesar, the Catuvellauni were in a continual state of war with the other tribes in the area.

Celtic Horned Helmet Found at River Thames Date 150-50BC
Caesar’s campaign in early July 54 BC was on a more massive scale. Five legions and 2,000 cavalry –some 27,000 men—were transported in over 800 vessels. The landing was unopposed. Mandubracius proved to be invaluable as a source of intelligence about the complexities of local politics and the principal centers of power in eastern Britain. He helped Caesar navigate through the terrain he would fight on. Armed with this information, Caesar made a rapid, though heavily opposed advance through Kent that let him to the Thames, which he crossed, probably near London.

Roman Cavalryman in Ancient Britain
Mandubracius was a political pawn that played to good effect for Caesar. The Trinovantes, whom Caesar describes as the strongest tribe in southeast Britain, sent a deputation to discuss terms for their surrender. In this agreement, Mandubracius was reinstated as the tribal king who Caesar promised to protect his sovereignty. In exchange, the Trinovantes surrendered to Caesar, sending forty hostages as an assurance of their good behavior and providing grain for the Roman army. The concession by the Trinovantes was the major turning point and other tribes quickly followed. In all likelihood the basic deal had already been negotiated during the winter, when Mandubracius was under Caesar’s protection in Gaul. Knowing that he could rely on the Trinovantes to come over to Rome would have emboldened Caesar to make his rapid advance into hostile territory across the Thames, dangerously far from his supply base.

Roman War Wagon Used in Ancient Britain
Cassivellaunus, King of the Catuvellauni
But the danger still existed for Caesar despite his settlement with the Trinovantes. His army made for Cassivellaunus’ oppidium (fortified town) of Verulamium in the vicinity of St. Albans. It was protected by forests and marshes, and a great number of men. Cassivellaunus sought the aid of four tribal kings in Kent to attack the Roman base and supply lines. The attack ultimately failed and there was little Cassivellaunus could do but negotiate for peace.
As it was late in the summer season, Caesar was eager to negotiate terms so he could return to Gaul. It was agreed the Catuvellanuni would pay an annual tribute to Rome and hand over hostages. Further, Cassivellaunus agreed to leave the Trinovantes in peace. With his primary aims achieved, Caesar returned to Gaul with a great many prisoners.

Ancient Ruins of Verulamium Wall near St. Albans
Julius Caesar Impact on Ancient Britain
Roman Domination
Whether these two brief excursions into Britain could be judged a Roman success is debatable since we do not know what Caesar’s true aspirations were for this isle. It is likely he had grossly underestimated the perils of the Channel crossing and the ferocity of the British resistance. He embarked on these expeditions with considerable risk and was lucky to escape with his reputation unscathed. What he did show, even if it was at a price, was the ocean could be mastered and that the distant island was accessible. He also claimed that the first step was taken to bring Britain under Roman domination. As far as Rome was concerned, southeast Britain had been conquered and treaty relationships had been established with the most powerful tribes. Britons were now paying an annual tribute to the Roman state. Others would have to complete the conquest.

Roman and Celtic Shields Used in Ancient Britain
Tribal Patronage to Rome
The Britons form the southeast gained not only first-hand experience of Roman military might, but, more importantly, they learned how the Romans had politically divided the tribes. Before the Roman invasion, the Celtic tribes were engaged in local conflicts and struck-up up allegiances for mutual benefit. Now these tribal rulers had a far more powerful force enter the arena. To gain patronage from the Roman world could offer them real advantages.

Celtic Gold Torc Worn by Celtic Leaders
The most important effect of Caesar on the British scene was to divide the southeastern tribes into pro- and anti-Roman groups. Those who had suffered defeat, i.e. the tribes on the north bank of the Thames and in Kent were forced to pay an annual tribute which sustained a festering hatred of Rome. Those who benefited, the Trinovantes and the Catuvellauni, were rewarded with political alliances and access to trade.

Peoples of Southern Britain According to Ptolemy’s Map
Lucrative trading monopolies were negotiated, and the hostages—usually young men from elite families—could be educated in Roman ways. Those who remained abroad maintained filial links with their tribe, while those who chose to return would bring with them new knowledge and a network of contacts that could benefit all. The desire to travel and to explore the world was deeply embedded in the psyche of the Britons. Patronage to the Roman cities was expanded.

Celtic child in frieze of Ara Pacis Augustae (Altar of Augustan Peace)
To be continued
The tribes that Caesar encountered in his first incursion that are mentioned above became powerful tribal kingdoms, in part, due to favorable treaties negotiated with Rome and favorable trading treaties. The subsequent rulers of these powerful kingdoms will be discussed in upcoming posts.
References:
Barry Cunliffe, Britain Begins; Oxford University Press, 2013.
Graham Webster, The Roman Invasion of Britain, Reprinted 1999 by Routledge (Imprint of the Taylor & Francis Group), NY.
Julius Caesar, translated by F. P. Long, The Conquest of Gaul; United States: Barnes & Noble, Inc., 2005.