Varus' forces included his three legions (Legio XVII, Legio XVIII, and Legio XIX), six cohorts of auxiliary troops (non-citizens or allied troops) and three squadrons of cavalry (alae).
 Most of these lacked combat experience, both with regard to Germanic fighters, and under the prevalent local conditions.
The Roman forces were not marching in combat formation, and were interspersed with large numbers of camp followers.
As they entered the forest northeast of Osnabrück, they found the track narrow and muddy.
 According to Dio Cassius a violent storm had also arisen.
He also writes that Varus neglected to send out reconnaissance parties ahead of the main body of troops.

The line of march was now stretched out perilously long—between 15 and 20 kilometres (9.3 and 12.4 mi).
It was in this state when it came under attack by Germanic warriors armed with light swords, large lances and narrow-bladed short spears called fremae.
The attackers surrounded the entire Roman army, and rained down javelins on the intruders.
Arminius, recalling his education in Rome, understood his enemies' tactics, and was able to direct his troops to counter them effectively by using locally superior numbers against the dispersed Roman legions.
The Romans managed to set up a fortified night camp, and the next morning broke out into the open country north of the Wiehen Hills, near the modern town of Ostercappeln.
The break-out was accompanied by heavy losses to the Roman survivors, as was a further attempt to escape by marching through another forested area, as the torrential rains continued.

The Romans undertook a night march to escape, but marched into another trap that Arminius had set, at the foot of Kalkriese Hill.
There a sandy, open strip on which the Romans could march was constricted by the hill, so that there was a gap of only about 100 metres between the woods and the swampland at the edge of the Great Bog.
The road was further blocked by a trench, and, towards the forest, an earthen wall had been built along the roadside, permitting the Germanic tribesmen to attack the Romans from cover.
The Romans made a desperate attempt to storm the wall, but failed, and the highest-ranking officer next to Varus, Legatus Numonius Vala, abandoned the troops by riding off with the cavalry.
His retreat was in vain, however, as he was overtaken by the Germanic cavalry and killed shortly thereafter, according to Velleius Paterculus.
The Germanic warriors then stormed the field and slaughtered the disintegrating Roman forces.
 Varus committed suicide, and Velleius reports that one commander, Praefectus Ceionius, surrendered, then later took his own life, while his colleague Praefectus Eggius died leading his doomed troops.

Roman casualties have been estimated at 15,000–20,000 dead, and many of the officers were said to have taken their own lives by falling on their swords in the approved manner.
Tacitus wrote that many officers were sacrificed by the Germanic forces as part of their indigenous religious ceremonies, cooked in pots and their bones used for rituals.
Others were ransomed, and some common soldiers appear to have been enslaved.

All Roman accounts stress the completeness of the Roman defeat.
The finds at Kalkriese of 6,000 pieces of Roman equipment, but only a single item that is clearly Germanic (part of a spur), suggests few Germanic losses.
However, the victors would most likely have removed the bodies of their fallen, and their practice of burying their warriors' battle gear with them would have also contributed to the lack of Germanic relics.
Additionally, several thousand Germanic soldiers were deserting militiamen and wore Roman armour, and thus would appear to be "Roman" in the archaeological digs.
It is also known that the Germanic tribes wore perishable organic material, such as leather, and less metal.

The victory was followed by a clean sweep of all Roman forts, garrisons and cities (of which there were at least two) east of the Rhine; the remaining two Roman legions in Germania, commanded by Varus' nephew Lucius Nonius Asprenas, were con
Varus' forces included his three legions (Legio XVII, Legio XVIII, and Legio XIX), six cohorts of auxiliary troops (non-citizens or allied troops) and three squadrons of cavalry (alae).  Most of these lacked combat experience, both with regard to Germanic fighters, and under the prevalent local conditions. The Roman forces were not marching in combat formation, and were interspersed with large numbers of camp followers. As they entered the forest northeast of Osnabrück, they found the track narrow and muddy.  According to Dio Cassius a violent storm had also arisen. He also writes that Varus neglected to send out reconnaissance parties ahead of the main body of troops.
The line of march was now stretched out perilously long—between 15 and 20 kilometres (9.3 and 12.4 mi). It was in this state when it came under attack by Germanic warriors armed with light swords, large lances and narrow-bladed short spears called fremae. The attackers surrounded the entire Roman army, and rained down javelins on the intruders. Arminius, recalling his education in Rome, understood his enemies' tactics, and was able to direct his troops to counter them effectively by using locally superior numbers against the dispersed Roman legions. The Romans managed to set up a fortified night camp, and the next morning broke out into the open country north of the Wiehen Hills, near the modern town of Ostercappeln. The break-out was accompanied by heavy losses to the Roman survivors, as was a further attempt to escape by marching through another forested area, as the torrential rains continued.
The Romans undertook a night march to escape, but marched into another trap that Arminius had set, at the foot of Kalkriese Hill. There a sandy, open strip on which the Romans could march was constricted by the hill, so that there was a gap of only about 100 metres between the woods and the swampland at the edge of the Great Bog. The road was further blocked by a trench, and, towards the forest, an earthen wall had been built along the roadside, permitting the Germanic tribesmen to attack the Romans from cover. The Romans made a desperate attempt to storm the wall, but failed, and the highest-ranking officer next to Varus, Legatus Numonius Vala, abandoned the troops by riding off with the cavalry. His retreat was in vain, however, as he was overtaken by the Germanic cavalry and killed shortly thereafter, according to Velleius Paterculus. The Germanic warriors then stormed the field and slaughtered the disintegrating Roman forces.  Varus committed suicide, and Velleius reports that one commander, Praefectus Ceionius, surrendered, then later took his own life, while his colleague Praefectus Eggius died leading his doomed troops.
Roman casualties have been estimated at 15,000–20,000 dead, and many of the officers were said to have taken their own lives by falling on their swords in the approved manner. Tacitus wrote that many officers were sacrificed by the Germanic forces as part of their indigenous religious ceremonies, cooked in pots and their bones used for rituals. Others were ransomed, and some common soldiers appear to have been enslaved.
All Roman accounts stress the completeness of the Roman defeat. The finds at Kalkriese of 6,000 pieces of Roman equipment, but only a single item that is clearly Germanic (part of a spur), suggests few Germanic losses. However, the victors would most likely have removed the bodies of their fallen, and their practice of burying their warriors' battle gear with them would have also contributed to the lack of Germanic relics. Additionally, several thousand Germanic soldiers were deserting militiamen and wore Roman armour, and thus would appear to be "Roman" in the archaeological digs. It is also known that the Germanic tribes wore perishable organic material, such as leather, and less metal.
The victory was followed by a clean sweep of all Roman forts, garrisons and cities (of which there were at least two) east of the Rhine; the remaining two Roman legions in Germania, commanded by Varus' nephew Lucius Nonius Asprenas, were con
Battle of the Teutoburg Forest