Superpowers like to think they are untouchable. But they should never forget the lesson of Britain's celebrated Boudicca, a guerrilla leader who struck fear into her conquerors, a new BBC programme reveals.
By Dan Snow
In AD60, Britannia - the Roman Empire's newest province - exploded into revolt.
After 17 years of occupation, a massive rebellion brought imperial rule to the brink of collapse.
An uprising was led by Boudicca, Queen of the Iceni. The Roman historian Cassius Dio, describes her as "most tall, in appearance most terrifying, in the glance of her eye most fierce, and her voice was harsh".
Boudicca's husband Prasutagus had signed a treaty with Rome that allowed him to keep a degree of autonomy over their tribal lands in today's Norfolk.
But when Prasutagus died, this cosy arrangement collapsed. Tacitus, a Roman historian whose father-in-law served in Britannia at the time, tells us that on Prasutagus' death Rome confiscated his kingdom.
Boudicca herself was flogged and, in a piece of horrific depravity, her young daughters gang raped.
At the time, the majority of Rome's forces in the province were in north Wales, busy crushing an army of Druids. So Boudicca had the ideal opportunity for revenge.
She led her tribe and other allies towards Camulodunum, today's Colchester, the capital of Britannia.
The town had no defences, and Boudicca's army burnt it to the ground and massacred the entire population, including those who tried to hold out in the massive temple of Claudius.
To make matters worse, the only Roman troops close enough to help were ambushed and annihilated by Boudicca as they raced to Colchester.
So in the space of a few days, the Roman capital had been destroyed and the only legion in the east of the province annihilated.
Come and have a go if you think you're hard enough
The Roman governor Suetonius Paulinus ordered his infantry to march back down Watling Street - which is now the A5 - while he went ahead with cavalry.
Meanwhile Boudicca moved towards the bustling commercial centre, Londinium, today's London.
Paulinus got to London before Boudicca, but quickly realised the hopelessness of his position.
London had no wall and was indefensible. That was a failing of the Romans: they believed that as the civilizing force - there to win the hearts and minds of Britons - that they needn't bother fortifying the cities.
After all, who would attack them? Certainly not the people they were there to enlighten.
So Paulinus ordered London's evacuation and rode north.
When Boudicca's army arrived in London, they slaughtered anyone who had been foolish enough to stay and burnt the town. Romans were tortured, hanged and skewered.
Wave of mutilation
Boudicca then took her turn up Watling Street, where she destroyed Verulamium, today St Alban's.
By this time, Paulinus had met up with his two legions that had been marching from Wales. Now he could stop Boudicca for good.
No one really knows where the battle was fought that would decide the fate of Roman Britain.
Some say Mancetter, others Towcester. Roman historian Tacitus describes the location that Paulinus chose as a "place with a narrow entrance, backed by woods". A narrow entrance would stop Boudicca's massive army from outflanking and encircling him.
But Paulinus had personnel issues. He must have been furious that the only other legion in Britannia, stationed in Devon, had failed to rendezvous with him. Now his 10,000 men stood alone against what Tacitus claims was a quarter of a million Britons.
The war chariots began the battle. They rushed forward while a warrior on the back hurled spears at the legionaries.
Meanwhile, the mass of Britons also charged. When they were 40 metres away the Romans threw thousands of javelins, which fell amongst the elite, front-rank British troops.
Where the javelins did not kill or injure they got caught in shields, which forced the Britons to discard them.
Then the Romans launched a second volley, this time with lighter javelins that travelled 15 metres. Again, the British troops fell but still others advanced upon the Roman lines.
Savage close combat ensued. The Romans' weapons and training were designed for exactly this situation. They rammed their large shields forward and stabbed their short swords to inflict hideous wounds.
Battle of Britain
Like the superpowers of today, it would be impossible for the Roman army to be defeated by conventional military means. The rebels would have to rely on acts of terror, such as the storming of supply areas, to weaken the Roman legions.
And in this battle, that did not happen.
Wagons, ho - families flocked to watch the battle
The Britons caught along the front lines were crushed by the mass of their own army. Their equipment was part of the problem: they were armed with long swords that needed room to swing. And in this tightly packed melee they could hardly move their arms.
So the Romans formed wedges that carved their way into the British ranks.
The Britons were jammed together, unable to resist the Roman killing machine as it pushed, stabbed and trampled its way forward.
To make matters worse, wagons had been placed in a semi-circle behind the army, where families could sit and watch the battle. Now these wagons penned the Britons in, blocking their only chance to escape Roman steel.
Tacitus claims that 80,000 Britons were killed, compared to losses of only 400 Romans.
The province had been saved. Boudicca herself probably took poison rather than fall into the hands of her enemy, and the Iceni were thoroughly 'pacified'.
Roman rule in Britain had faced its sternest test. Had Paulinus been defeated it is likely that the Romans would have permanently withdrawn from Britain.
Battlefield Britain was broadcast on 6 August at 2100 BST on BBC Two.