After leaving the towns of Londinium and Verulamium unchallenged to Boudicca's rebel army, Suetonius prepared his terribly outmanned force in the forest of the midlands. (Ancient sources give estimates as greatly divergent as 200,000 to 10,000, but this is most assuredly wild propaganda on the part of Tacitus and Dio Cassius.) However, the Romans had the advantage of their classic discipline, and tactical use of geography. Boudicca and her army were also slowed down by the 'barbarian' tradition of traveling with entire clans, including women, children and the elderly (possibly partially accounting for the inflated army size, with non-combatants not being excluded from the 'army'). Much like any other army, they were also weighed by livestock and pack animals, certainly an enormous number of wagons and transport vehicles, all probably filled to the brim with personal belongings and various loot pillaged at the expense of the Roman villagers. As the massive Celtic force approached Suetonius and his legions, it was the Romans who held the advantage. To this point, though the damage the Iceni and their allies had caused was great, Boudicca's army had not faced prepared and disciplined Roman soldiers in any effective number.
Tacitus, in the glorifying style of the ancients, provides an assuredly fictitious account of Boudicca's speech, but one that likely captures the feelings of the moment.
"Boudicca, in a chariot, with her two daughters before her, drove through the ranks. She harangued the different nations in their turn: "This," she said, "is not the first time that the Britons have been led to battle by a woman. But now she did not come to boast the pride of a long line of ancestry, nor even to recover her kingdom and the plundered wealth of her family. She took the field, like the meanest among them, to assert the cause of public liberty, and to seek revenge for her body seamed with ignominious stripes, and her two daughters infamously ravished. From the pride and arrogance of the Romans nothing is sacred; all are subject to violation; the old endure the scourge, and the virgins are deflowered. But the vindictive gods are now at hand. A Roman legion dared to face the warlike Britons: with their lives they paid for their rashness; those who survived the carnage of that day, lie poorly hid behind their entrenchments, meditating nothing but how to save themselves by an ignominious flight. From the din of preparation, and the shouts of the British army, the Romans, even now, shrink back with terror. What will be their case when the assault begins? Look round, and view your numbers. Behold the proud display of warlike spirits, and consider the motives for which we draw the avenging sword. On this spot we must either conquer, or die with glory. There is no alternative. Though a woman, my resolution is fixed: the men, if they please, may survive with infamy, and live in bondage."
To not be undone by his female rival on the approach, Suetonius' speech was equally 'recorded' by Tacitus.
"Suetonius, in a moment of such importance, did not remain silent. He expected every thing from the valour of his men, and yet urged every topic that could inspire and animate them to the attack. "Despise," he said, "the savage uproar, the yells and shouts of undisciplined Barbarians. In that mixed multitude, the women out-number the men. Void of spirit, unprovided with arms, they are not soldiers who come to offer battle; they are bastards, runaways, the refuse of your swords, who have often fled before you, and will again betake themselves to flight when they see the conqueror flaming in the ranks of war. In all engagements it is the valour of a few that turns the fortune of the day. It will be your immortal glory, that with a scanty number you can equal the exploits of a great and powerful army. Keep your ranks; discharge your javelins; rush forward to a close attack; bear down all with your bucklers, and hew a passage with your swords. Pursue the vanquished, and never think of spoil and plunder. Conquer, and victory gives you everything."
Both armies thus inspired for the battle, the Iceni advanced with great ferocity on the tightly formed Romans and pelted them with spears. However, because of the narrowness of the battlefield, being surrounded by forest, the incredible numbers of the Britons were not able to come to bear, and the Romans were able to turn the tables. Tightly formed they maneuvered into a wedge enabling the best possible strategy for the conditions. Hammering the Celts with javelins, Suetonius followed up with waves of brutally effective auxilia and regular infantry charges. By the ancient accounts, the Roman assault was overwhelming, and the Britons were crushed in the onslaught. Perhaps as many as 80,000 of Boudicca's rebels were killed in the immediate aftermath, with the Romans killing women and children indiscriminately. By contrast, Tacitus reports that only 400 Romans were killed, and an equal number wounded, in the battle.
Boudicca may have initially escaped, along with an undetermined number of warriors and civilians, but it wasn't long before the victorious Romans followed up their victory with continued slaughter. Even before the battle, reports indicate that the revolting Iceni had failed to sow their crops for the season, and only their looting would provide sustenance for the winter. Without that loot thousands would perish of starvation. In addition, the Romans hastened this fate by laying waste to Iceni lands in an obvious attempt to set an example. They were further subjected to natural atrocities of all kinds, and sold en masse into slavery.
Suetonius, though criticized in part for not facing Boudicca sooner, returned to Rome to receive victorious honors from Nero. As for Boudicca, rather than face humiliation marching in a Roman triumph, she took her own life via poison. If her daughters survived the initial battle, they too disappear from the historical record at this point. The Iceni queen is often revered today as a great freedom fighter against Roman oppression, but this view must be tempered by the stark contrasts in time periods and motivations. Regardless of the truth for the inspiration behind Boudicca's revolt (the rape of her daughters and her own whipping, or the complete subjugation of her lands), her acts of vengeance are no less brutal Roman tactics. Though she did aggressively punish small contingents of Roman legionaries, the main focus of Iceni aggression was the wholesale slaughter of Roman civilians. In the first major conflict against a sizeable Roman force, the Iceni were effectively eliminated, and with them, so was resistance to Roman rule in all of southern Britain. Though it would still take another generation, and the governorship of Agricola 20 some odd years later to stretch Roman hegemony into modern Wales and to the borders of Caledonia, the death of Boudicca ushered in the Romanization of the province.