The Battle of the Teutoburg Forest.

The year is AD 9. A serious rebellion is underway in Illyricum (the Balkans), a crucial province of the empire. Half of the empire's entire military force is in Illyricum, desperately pacifying the region. Augustus' greatest generals, including his stepson, the future emperor Tiberius, are there as well.

Meanwhile, on the other side of the empire in Germania (roughly western Germany and the low countries), Publius Quinctilius Varus is charged with completing Germany's integration into the Roman state. With half of the empire's forces in Illyricum, Varus has a mere three legions at his disposal: Legio XVII, Legio XVIII, and Legio XIX, about 36,000 troops. Varus was a ruthless and decorated commander known for crucifying his enemies. He was well-known among the German tribes.

To aid him in his subjugation of the Germans, Varus relied on a German-born advisor, Arminius (a latinization of Hermann). Arminius had been sent to Rome as a hostage by his father many years before, and had grown up to be a competent statesman with great leadership potential. But despite his thorough romanization - despite his Roman education and upbringing - Arminius bore a deep hatred for Rome and vowed secret revenge.

Using Varus' cruelty as an exemplar of life under Roman rule, Arminius secretly allied himself with many disparate tribes, most of whom had been ancient, irreconcilable enemies. For you Game of Thrones fans out there, think of him as a Mance Rayder, 'King Beyond the Wall' type. This included tribes that had already surrendered to Rome and lived within Roman-controlled Germania as allied tribes.

One day, Arminius manufactured false reports of a rebellion in a critical area of Germania. He presented the situation to Varus as one which required his immediate and personal attention. Of course, the urgency of the crisis required Varus to march his entire force through an area unfamiliar to the Roman troops - but no worry; Varus can rely on his trusted German advisor, can't he?

Segestes, another Roman advisor - father-in-law to Arminius and Arminius' political rival - warned Varus the night before the march to battle that the entire crisis was a fabrication, and that Varus should seize Arminius and certain key Germans whom Segestes identified as core members of a conspiracy But Varus was assuaged by assurances from others that this was merely a lie borne from Segestes' rivalry with Arminius.

The army set out - but not in battle formation. In a line stretching nearly 20 km long, greenhorn soldier rubbed elbows with unarmed camp follower through a dark and murky swamp. Not a single reconnaissance party marched in advance. As a violent storm broke overhead, German troops surrounded the Roman train entirely.

With his Roman education, Arminius was unique among the German leaders present at the battle: he had been trained in Roman tactics. Observing Roman behaviour throughout the battle, Arminius recognized every by-the-book strategy and directed his forces to employ the correct, Roman-approved countermove.

Massacred and in disarray, the Roman survivors fled into the night - for the battle lasted beyond sundown - and reached a place now identified by archaeologists as Kalkriese Hill in Lower Saxony. Alas, too late did the Romans realize that they had been herded to this very place like sheep: a network of earthen walls, trenches, and German units bristling with Roman-made armour and weaponry awaited them.

Varus and at least one other commander fell on their swords, either during the battle or after their capture. Another commander took charge of the cavalry and, on horseback, attempted to flee - but they were all cut down. One commander, a certain Praefectus named Eggius, stood his ground and fought to the last man, to his death.

The few commanders who did not fall on their swords were given up in human sacrifice by the Germans, who practiced human sacrifice at this time. Shame upon shame, the three golden eagle sculptures - the standards of the legions - were lost to German hands.

The Roman defeat was utter and total. German hordes flooded across Germania, chasing terrified Roman troops and settlers to the Rhine. The Romans would never again conquer Germany directly; the Rhine was the new, permanent border of the Empire. Only by appointing client kings would Rome ever attempt to control Germania again.

Augustus himself banged his head against the walls of his palace, screaming, "Quinctilius Varus, give me back my legions!"

The three legion numbers were retired and never used again. It was not until AD 14 that a punitive expedition was sent out; two of the three lost eagles were recovered, and victory was declared. The third standard would be recovered in a raid nearly thirty years later.

An epilogue: forty-one years after the battle, the last survivors of Varus' army were freed from German slavery when they were discovered unexpectedly after a battle with a German tribe called the Chatii.