The First Veientine War (483-474 B.C.) was the first of three clashes between Rome and her nearest Etruscan neighbour, the city of Veii. The two cities were only separated by ten miles, and had almost certainly fought a series of wars before this first clearly recorded clash.
The two powers' territories were almost a mirror image of each other. Most Roman territory was on the left bank of the Tiber, most Veientine territory on the right, but both cities controlled part of the opposite bank - the Romans an area on the coast, which stopped the Veientines from freely using the Tiber to reach the sea, and the Veientines the city of Fidenae, five miles upstream from Rome. Control of Fidenae also gave Veii control of a convenient crossing point over the Tiber.
Soon after the formation of the Republic the Romans began to expand north. Fidenae was captured (probably in 498 B.C.), and Roman colonists sent to settle the area. The Veientines still controlled a crossing point further upstream at Lucus Feroniae, but this was not so convenient.
The exact course of the war is unclear. Roman sources claim that they won a victory in 480 B.C., and most of the known fighting took place on the right bank of the Tiber. In 479 B.C. one Roman clan, the Fabii, established a fort in the Cremera Valley, between Veii and the Tiber, just after the Veientines had built their own fort on the Janiculum hill, opposite Rome.
In 477 B.C. the Veientines attacked the Fabian fort, killing all but one of the 307 members of the clan and their clients in the fort (the survivor, Q. Fabius Vibulanus, became consul in 467 B.C.). This disaster was balanced by the Roman capture of the fort on the Janiculum. Livy records another battle close to Veii, in which the Romans overran a Sabine camp and defeated a Veientine attempt to help their allies. In the following year Veii asked for a forty year truce, which was granted, bring the war to an end. Fidenae may have remained under Veientine control at the end of this war, although according to Livy it was a revolt in that city that triggered the second Veientine War, forty years later.