At approximately 7:00 AM on the morning of September 8, in 9 AD, a Roman force of nearly 22,000 broke camp and departed from their planned route westward along the northern side of the Lippe River to their home base at Vetera (Xanten), west of the Rhine. Instead, the Romans were led northwest into the Teutoburg Forest by Arminius and his cavalry cohort lieutenants. Arminius quickly made the excuse to leave with most of his cavalry to protect the Roman right flank and gather allied tribal forces. Some of his cavalry leaders undoubtedly remained to lead the Roman column along their planned route of piece by piece annihilation. The column was allowed to get far enough into the forest, where it was beyond the point of return. The narrow and winding column of Roman legions and their auxiliaries stretched to over nine miles. It was much slower and harder going than represented by Arminius. The Romans were exhausted by the rugged terrain and having to fell trees and remove obstacles.
Before leaving the Lippe, Varus had sent a small detachment of the 19th Legion under Prefect Lucius Caedicius on their originally planned route to prepare a campsite near the Roman outpost at Aliso (Haltern) just east of the Rhine. A Prefect was a field grade Roman officer in charge of setting up and managing legion campsites.
Once the legions, their attached cohorts and cavalry, and baggage train were beyond the point of no return, the Bructeri, who had been positioned along the ambush route planned by Arminius, began to launch hit and run attacks on the Roman column. The Roman route paralleled a ridge on its left flank. Most of the Bructeri attacks assaulted the Roman column from higher sloping ground on this left flank, using mostly spears, axes, and short swords, and quickly withdrawing before the stunned Romans could organize disciplined resistance. The Bructeri sometimes managed a surprise attack from the right flank or both flanks. The nature of the terrain made traditional Roman responses to ambush extremely difficult. The Bructeri objective was to destroy supplies and inflict casualties, leaving the Romans to care for many wounded. Roman counter-attack into the forest would have been sure death.
In the late afternoon, torrential rains added to their already growing problems. The column trudged on, however, at a slower but exhausting rate. If it were not for the Pioneers (combat engineers), they could have made no progress at all. At last they reached a clearing and made camp, including a traditional stockade fitted to the terrain as best possible.
Varus and his key officers met for several hours that night. Although communication along the long column was poor, they believed (perhaps wrongly) that casualties had been comparatively light. The German objectives seemed primarily to throw them off balance, delay their progress, and wear them out. Varus and his officers were primarily concerned about how much the baggage wagons were slowing them down, and a few were growing anxious about the whereabouts of Arminius and his promised reinforcements.
On the morning of September 9, the rain continued, visibility in the forest was low, and the trail ahead was a sea of mud, shallow pools, and fallen trees. Varus decided not to march until the rain ended. They sent out two reconnaissance patrols, one south to find Arminius, and one north and west to explore the practicality of moving forward. The patrol to the south never returned. One source, connecting the dotted lines, speculates that Arminius and his cavalry were following close behind to close the rear end of their trap. That source speculates that the patrol was taken prisoner by Arminius, interrogated, and killed. The larger northern patrol found that the path forward had large tracts of glutinous mud that would make passage by infantry, cavalry, and mules difficult but passable and impassable for wheeled transportation. A western deviation would have to cross a ridge, making it even more impractical.
On September 10, the Romans broke camp before daylight, leaving their wounded behind with medics and a small guard force. They decided to abandon and destroy the heavier wheeled wagons and load as much of their cargo as possible on mules. They marched on continuing to trudge through mud, removing downed trees and limbs as they went.
Meanwhile Arminius’s cavalry cohort came upon the civilian baggage train, the abandoned wreckage of Roman wagons, and the small force protecting the Roman wounded. The Roman soldiers including wounded were presumably killed.
Arminius immediately ordered the baggage train to be burned, but many of his Cheruscan cavalry cohort wanted to loot it. This turned into a leadership crisis for Arminius, who knew that stopping to loot the baggage would cause enough delay and distraction to endanger their mission to destroy the Roman legions. Heated words were spoken, but Arminius was able to convince them to stay on strategy. Some asked if they should kill the women and children, and he is reputed to have told them that “Germanic warriors do not make war against women and children.” They were not killed. Most were probably held as valuable hostages, ransomed, or enslaved.
By dawn, the German ambushes continued but with astonishing and deadly fury. Roman casualties were heavy, especially their officers. By early afternoon, they veered northwest to a clearing that would make an ideal campsite. They encamped there and put up their usual stockade encirclement.
Varus’s afternoon staff meeting revealed that two legion commanders had been killed, and that all but a remnant of the 19th, Legion, marching as the rear guard, had been wiped out. As much as two-thirds of the foreign auxiliary cohorts had either deserted or joined the enemy. Less than 8,000 men were fit for combat. To be continued.