In the Second Punic War, the Boii and Insubres allied themselves with the Carthaginians, laying siege to Mutina (Modena). In response, Rome sent an expedition led by L. Manlius Vulso. Vulso's army was ambushed twice, and the Senate sent Scipio with an additional force to provide support. These were the Roman forces encountered by Hannibal after his crossing of the Alps. The Romans were defeated in the Battle of the Ticinus, leading to all the Gauls except for the Cenomani to join the insurgency. Rome then sent the army of Tiberius Sempronius Longus who engaged Hannibal in the Battle of the Trebia, also resulting in a Roman defeat, forcing Rome to temporarily abandon Gallia Cisalpina altogether, returning only after the defeat of Carthage in 202 BC.