But this was no simple conflict between Romans and Barbarians. It was one small part of the complex civil war we call The Year of the Four Emperors. The Batavians, who lived around the mouth of the Rhine and had their capital on an island there, had been Roman allies since 43 AD and had sent thousands of men to assist in the conquest of Britain. Their leader in 69 is known to history as Gaius Julius Civilis, a moniker he probably assumed to emphasize his loyalty to the Julio-Claudian dynasty and his status as a Roman citizen.
He was both the hereditary king of the Batavi and the hereditary commander of their troops in Roman service. He somehow fell foul of Nero's regime like a lot of other people , his brother was executed, and he was sent to Rome in chains to be judged by the emperor. Understandably, when revolt against Nero broke out under the leadership of Galba, Civilis and the Batavians supported the revolt.
After more intrigues, the Batavi ended up supporting the Roman general Vitellius, and the Batavian cohorts helped him win the Battle of Bedriacum and become emperor himself in April But the Batavi felt ill-used by Vitellius; in one of his imaginary speeches, Tacitus has their commander say "That in truth they were no longer held as confederates, but treated like slaves. Tacitus: "As with mighty concurrence he was heard, he bound them all in a combination, solemnized with barbarous usages, with maledictions and imprecations peculiar to the country.
But the legions along the Rhine remained loyal to Vitellius, so it was as part of a Roman civil war that imperial legions and barbarian horseman happened to fight that December. The Batavians were actually organized as Roman troops, eight cohorts of allied cavalry and several cohorts of infantry as well. The fight took place outside a Roman fort called Gelduba, within which two Roman legions had been besieged after an earlier battle. When a force came to relieve them they marched out to do battle.
According to Tacitus, the Batavian cavalry broke through one Roman legion "with the hideous chanting of the men, and the howlings of the women" and seemed to be winning the battle, when timely Roman reinforcements arrived in their rear, leading to their defeat, with great slaughter.
