In 400 BCE, they crossed the Alps and, driving out the Umbrians, settled on the east coast of Italy. Their territory spanned from Forlì to Ancona and Terni, in the "Ager Gallicus". They founded the town of Sena Gallica (Senigallia), which became their capital. In 391 BCE, under the chieftain Brennus, they invaded Etruria and besieged Clusium. The Clusines appealed to Rome for aid. The Romans provided support, which constituted a violation of the law of nations. The ensuing war resulted in the defeat of the Romans at the Battle of the Allia (18 July 390 BCE) and the sacking of Rome.