The battle of the Vingeanne (July 52 B.C.) was a cavalry battle that saw the Romans and their German auxiliaries defeat a Gallic attack on their column, a defeat that may have been the main reason that Vercingetorix chose to defend the nearby town of Alesia.
In the summer of 52 B.C. Julius Caesar was faced with the most serious crisis of the entire Gallic War. A coalition of the tribes of central and north-western Gaul, under the leadership of Vercingetorix, had risen in revolt. Caesar had managed to rejoin his legions in their winter quarters in the north, and had captured a series of towns, most importantly Avaricum. Caesar then led six of his ten legions against Gergovia, but before the siege had really begun the revolt had spread to the Aedui tribe, Rome's oldest allies in Gaul. Caesar was forced to abandon the siege of Gergovia and move north to reunite his army, probably meeting up with the four legions under Labienus somewhere in the vicinity of Agedincum (Sens).
Vercingetorix's next move was an attack on the Roman Province of Transalpine Gaul, which was defended by twenty-two cohorts of infantry – the equivalent of just over two legions – spread out along the entire frontier.
Caesar had already begun to recruit German cavalry, using four hundred of them at Noviodunum earlier in the year, but the revolt of his main Gallic ally forced him to hire more cavalry and light infantry from across the Rhine. Caesar himself claimed that these troops came from the states that he had subdued in previous campaigns, but paid auxiliaries seems more likely.
Caesar led his reunited army east, through the lands of the Lingones towards those of the Sequani, on a route that probably took him down the Vingeanne valley (the Vingeanne is a western tributary of the Saone). His stated intention was to move into a position from where he could support the defenders of the Roman Province. Vercingetorix and the main Gallic army were close by, and on the day before the battle camped about ten miles from the Romans.
Caesar gives a report on the speech Vercingetorix used to encourage his cavalry to attack the Roman column. Given that Caesar's men captured a number of senior Gallic leaders during the fighting, the outline of Vercingetorix's argument is probably accurate. The Gauls clearly believed that the Romans were evacuating Gaul, and Vercingetorix had to convince his men that it was worth risking an attack on a retreating army. His argument was that if Caesar was allowed to escape with his army intact then it was inevitable that he would return with greater forces. He argued that the Gallic cavalry should attack the Roman column while it was marching, forcing them to either stand and fight, thus abandoning their planned retreat, or abandon their baggage and attempt to fight their way through the Gauls. The cavalrymen were won over and swore an oath not to be 'received under a roof, nor have access to his children, parents or wife, who shall not twice have ridden through the enemy's army'.
Vercingetorix had good reasons to be confident about the results of a clash between the weak Roman cavalry and his own increasingly strong cavalry force. His Gallic allies had provided Caesar's best cavalry in earlier campaigns, and most of them were now with Vercingetorix. It would be Caesar's German cavalry that made the difference during this battle.
The attack came on the day after Vercingetorix's speech. He split his cavalry into three divisions. The central division attempted to obstruct the Roman march while the other two divisions demonstrated against the Roman flanks.
Caesar responded by splitting his own cavalry into three divisions and ordering them to charge the Gauls. The Gauls must have had some initial success, for Caesar describes how he moved the legions to support any of his men who were hard pressed or distressed, but eventually the German cavalry on the Roman right fought their way to the top of a hill, dislodged their Gallic opponents and pursued them all the way back to Vercingetorix and the Gallic infantry, on an unidentified river.
Seeing this, the other two Gallic divisions broke and fled, with the Roman cavalry in pursuit. During this final phase of the fighting the Romans captured three senior Aeduan, including Cotus, their cavalry commander, Cavarillus, their infantry commander, and Eporedorix, a former leader who earlier had warned Caesar about the initial outbreak of rebellion.
After the failure of the cavalry attack Vercingetorix decided to abandon his current camp, and led his men towards Alesia. Caesar left two of his ten legions to guard the Roman camp and led the other eight in a pursuit in which he claimed to have killed three thousand Gauls. On the next day Vercingetorix entered the town and the Romans camped outside it, starting the siege of Alesia, the decisive engagement of the entire Gallic War.