Once word went out that the uprising had begun, the small units of Romans that Arminius had got Varus to scatter through the countryside were quickly surrounded and massacred.

But it was the main column of Varus' army that Arminius knew he had to destroy. This consisted of three legions - the Seventeenth, Eighteenth and Nineteenth - several thousand auxiliaries and support troops and a gaggle of colonists, traders, scouts, campfollowers and women and children.

Varus was heading through the Teutoburgerwald, which consists of heavily wooded land cut with deep ravines. They were probably using a Roman-built log road, but in places it would have been little more than a track, and the column was strung out over several miles and broken up by baggage trains. They were still in friendly Cherusci territory (supposedly) so they wouldn't have been marching in defensive deployment as they would in hostile country. To make matters worse, a huge autumnal thunderstorm broke with torrential rains and high winds which brought down trees, slowing the march further.

It was then that Arminius struck. His own Cherusci cavalry - auxiliary troops marching with the column and probably leading it - hit first. They would have turned on their Roman comrades and attacked without warning, spreading confusion and snarling up the march.

Then, from all sides, the main Cherusci warband and their allies attacked. They made a point of not closing with the Romans - preferring hit and run guerilla tactics. They would strike, shower the disorganised column with spears and then disappear back into the forest.

The Germanics used their knowledge of the terrain to their advantage, using secret paths and hunting techniques to constantly harassing wear the Romans down. The Romans became completely disoriented - blinded by rain, attacked from all sides, their shields so waterlogged they could barely be used. Slowly, as the first and then the second day wore on, the army was worn down and eventually broken up.

By the beginning of the second day of the battle, Varus had regained some control. He ordered most of the baggage train to be burnt or abandoned - both to speed the march up and, perhaps, to distract the Germanics with the prospect of loot. Then the column set off again in slightly better order, this time heading south-west for the safety of the fortress of Aliso on the River Lippe.

Crossing some open country, they made better speed, but they soon entered heavy woods again and once again the attacks began on all sides. One attempt to regroup and break out failed and once again the column became disrupted.

On the third day, all order was breaking down. The weather had worsened again and the going was tougher than ever. The column was now probably reduced to disconnected bodies of men - many of them leaderless - while news of Arminius' success was spreading and more and more warriors were joining in the fight. At some point Numonius Vala, Varus' cavalry commander, decided enough was enough. Abandoning the infantry he and his troopers made a break for it and tried to ride west to the Rhine. Germanic cavalry pursued them and none of the Vala's men ever got to the frontier alive.

By this stage Varus could see the end was nigh. It's likely that the remnant of the army that he still had around him were, at this stage, rounding the north of the Kalkrieseberg, near modern Osnabruck. Using a path between the high hill and a swamp, they were trying to sneak past the Germanics around them, muffling the harness of their pack mules with twists of grass.

But they didn't realise that they were walking into Arminius' last trap - a prepared killing ground.