Caesar had been appointed to a governorship over a region that ranged from southern Gaul to Illyricum (but not Italy). As his term of governorship ended, the Roman Senate ordered Caesar to disband his army and return to Rome. He was explicitly ordered not to bring his army across the Rubicon river, which was at that time a northern boundary of Italy. In January of 49 BC, Caesar brought the 13th legion across the river, an act that was considered insurrection, treason, and a declaration of war upon the Roman Senate.