The Roman province of Britannia very nearly collapsed in the Boudiccan Revolt in AD 60-61.
Boudicca was the Queen of the Iceni after her husband, who was an ally of Rome, died. The Iceni were actually a client state to the Romans. The Romans never bothered at that stage to conquer the far north of East Anglia (north Norfolk) because the Iceni were a client state and friends of Rome.
In his will Boudicca’s husband had set out that his daughters would inherit his kingdom, but the Romans, being the Romans, ignored this.
When the king died, the Romans wrapped the kingdom of the Iceni into the province of Roman Britain. This ignited a huge rebellion, which became this enormous conflagration across the entirety of the southeast, down to the line of the Thames.
Interestingly, the Cantiaci in Kent didn’t join in. Certainly, the Iceni, the Catuvellauni, and the Trinovantes in the southeast above the line of the Thames joined in, and it became a cataclysmic rebellion going from north to south through East Anglia.
What did the revolt achieve?
Firstly, these 100,000 warriors (within a body of 250,000 individuals) arrive in Colchester, defeating on the way an attempt from Legio IX Hispana to try and stop them. Torching Colchester, which was set up by Claudius as the capital of the province after the AD 43 invasion, they murdered and burnt all of the refugees in the Temple of Claudius.
After also torching London, they followed the line of Watling Street, the great military trunk road of Roman Britain. It went through Richborough, Rochester, London and St. Albans, to the Welsh Marches, and then north to Chester and south to Caerleon in southeast Wales.
Boudicca’s army followed the line of Watling Street up to St. Albans, torching it too. Just above St. Albans, probably near where the M1 is today, they found their path blocked by the Roman Governor, Paulinus.
How was it defeated?
Paulinus was successfully campaigning in Anglesey when he heard about the revolt and marched what limited troops he had (only one legion and elements of another) the other way down Watling Street, to stop Boudicca in her tracks.
Let’s consider the numbers of soldiers here. The probability is that Paulinus, the warrior governor, only had about 10,000 troops – both legionaries and auxiliaries. Boudicca may have had 100,000 warriors and within a body of 250,000 people. Still, Paulinus fights a spectacularly successful battle by choosing his ground very carefully.
He selects a bowl-shaped valley where he can put his defence on the upper slopes at the end of the valley, which has wooded sides to defend the flanks. Therefore, when the mass of Britons comes into this bowl-shaped valley, they become compressed. Then the legionaries launch their attack with their pila (javelins) and then their gladii (swords), and they slaughter the Britons.
The Britons are defeated, Boudicca commits suicide, and the province is saved; but only by the skin of its teeth.
One of the outcomes is the Romans move the provincial capital from Camulodunum, Colchester, down to the growing city of London, and the province starts to develop from that point.