“Quinctilius Varus, where are my eagles?!!!” is what Brian Blessed’s Emperor Augustus exclaims, in the BBC Classic “I Claudius”, upon hearing of the battle of the teutoburg forest, which took place on this day, September 9th, 9AD.

The battle was the most catastrophic defeat the Roman Empire would suffer for several centuries. Three Legions, and all their men, were killed. General Quinctilius Varus committed suicide. Rome’s power on the Rhine was broken, and it never attempted to invade Germany seriously again.

And it was all accomplished with an act of betrayal. The German General, Arminius, was serving on the Roman staff. As a boy, he had been taken hostage by Rome and raised as a Roman. He knew the Romans, and their military secrets, and he was trusted by the Roman Generals.

In 6AD, Arminius was appointed as an advisor to Varus, who trusted him implicitly. But all the while, Arminius, under the guise of conducting diplomatic missions on behalf of Rome, was assembling the German tribes into an alliance against Rome, and plotting the destruction of the Roman Army in Germany.

In 9AD, he sprung the trap. Varus was told, by Arminius, of a rebellion taking place in Northern Germany. Varus was advised to march his three legions north in a show of force, and, trusting Arminius completely, he did just that.

He marched his men through the dark Teutoburg forest. Thousands of them, marching three men abreast, in a line that stretched for several kilometres. In this state, they were unable to form up for battle, or communicate properly.

The Germans, knowing that they were coming, were able to attack them along a front that was kilometres long, and from both sides at once. Unable to communicate or organise, the Romans were separated, divided, and slaughtered en masse.

Almost thirty thousand were killed, or taken prisoner. Many of these were later sacrificed to the German Gods. All three eagles – the standards of the Legion, and precious to Rome – were captured.

The consequences of the battle were significant: Rome, having lost a good fifth of her entire army, was no longer able to maintain a presence in Germany. While Tiberius, who would later succeed Augustus as Emperor, did conduct some punitive raids in the coming years to get revenge, Roman influence never again extended beyond the Rhine.

The Eagles were eventually recovered in the reign of the Emperor Claudius, but they stayed in German hands for over fifty years. It was the one great humiliation, and defeat, of the Emperor Augustus’s reign, and one which is said to have wounded him personally, to a degree that he never truly got over it. He died four years later.

The battle of the Teutoburg Forest, on this day, September 9th, 9AD.