According to Caesar's report, a combination of determined defence, skilled generalship, and the timely arrival of reinforcements allowed the Romans to turn a strategic defeat into a tactical victory.

During the winter of 58–57 BC rumours came to Caesar's ears that the Belgae tribes were forming a union because they feared possible Roman interference in their affairs.

In the face of this and because of shortage of provisions, the union collapsed and tribal armies retreated to their own lands, with the agreed future intention of coming to the support of any tribe invaded by the Romans.

A fierce and brave tribe, they did not allow the import of luxury items as they believed these had a corrupting effect and probably feared Roman influence.

A Roman legion during this era had a theoretical strength of some 4,800 fighting men with additional auxiliary forces (usually skirmishers and cavalry).

Eight Roman legions plus an unknown number of auxiliary (skirmishers: archers, slingers and javelinmen) and allied cavalry are recorded to have taken part in the battle.

It is not known if the legions were at full strength, but a reasonable estimate for Caesar's army might be in the range of 30,000–45,000 fighting men (including skirmishers and cavalry).

Caesar claims he had earlier received intelligence from the Remi that the various tribes of the Belgae had promised to contribute a total of 300,000 fighting men.

Roman Republic – Julius Caesar's eight legions: VII, VIII, IX Triumphalis, X Equestris, XI, XII Victrix, XIII, XIV – auxiliaries: slingers, archers, javelinmen and cavalry.

He learnt from prisoners taken later that sympathisers in the ragtag of surrendered Belgae and other Gauls travelling with the army had gone to the Nervii and reported the disposition of his column.

The Nervii, having traditionally always relied on infantry rather than cavalry, had over the years developed a technique of building dense, impenetrable hedges of briars and thorns set between young trees as a defence against the raids of surrounding tribes.

The top of that hill was densely wooded but the lower part was open and sloped down to the river over a distance of 200 paces (roughly 300 metres (330 yd)).

He does not elaborate further so it will never be known if the Nervii were trying to entice the skirmishers onto their hidden position or holding them in play on the slopes in preparation for the planned rush.

They crossed the shallow river at full speed and charged up the hill against the legions setting up camp, giving them no time to get into battle formation.

It seemed to Caesar that the Nervii came on with incredible speed, all at once pouring out of the trees, charging across the river and overrunning his legionaries.

[17] Caesar states that the hedges were a considerable obstruction to his men during the battle, although he does not specify their locations on the field,[18] but the woody hilltop is the one place we can infer their presence.

The soldiers of legions X Equestris and IX Triumphalis on the left flank, having thrown their pilae at their Atrebates opponents, charged.

Even the usually-dependable Treveri cavalry arriving to support the Romans looked at the seemingly hopeless situation and promptly turned for home to report the disaster.

Caesar does not detail their actions, but they probably cleared the camp (as it was their nearest target) and went to the right to relieve the pressure on Legions XII and VII.

Seeing the position begin to stabilise, cavalry and skirmishers took heart and, keen to wipe out their earlier shame, started to fight in earnest.

Using peltasts (a light infantry) equipped with slings and javelins, and with the help of archers, they unleashed a barrage of missiles at the closely packed Nervii.

The Nervii warriors fought to the last, standing on the bodies of their slain comrades, and throwing the Romans’ own spears back at them.

[24] Caesar talks of a grimly inspiring image of the last of the Nervii who were atop a mound of corpses of their own warriors and shouting in defiance towards the Romans, fighting till their last breath.

While Caesar appears to give a relatively frank account of the course of the battle, in The Conquest of Gaul, this remains one of the only primary sources.

And since it was written by Caesar, much is unknown of the Nervii's perspective, such as the extent to which Boduognatus planned the attack and directed his forces during the battle.

[29][30] The Veneti, the Unelli, the Osismii, the Curiosolitae, the Sesuvii, the Aulerci and the Rhedones were all brought under Roman control following the battle.

[32] During Vercingetorix's revolt (52 BC) the Nervii were only asked to supply 5,000 men to the forces raised by a confederation of over forty tribes.