In 101 BC, the Cimbri returned to Gaul and prepared for the final stage of their struggle with Rome. For the first time they penetrated through the Alpine passes, which Marius's co-consul for that year, Quintus Lutatius Catulus, had failed to fortify, into northern Italy. Catulus withdrew behind the Po River, leaving the countryside open to the invaders. But the Cimbri took their time ravishing the fertile region, which gave Marius time to arrive with reinforcements — his same victorious legions from Aquae Sextiae. It would be at Vercellae near the confluence of the Sesia River with the Po on the Raudine Plain where the superiority of the new Roman legions and their cavalry were clearly demonstrated. In the devastating defeat the Cimbri were virtually annihilated, and both their highest leaders, Boiorix and Lugius, fell. The women killed both themselves and their children in order to avoid slavery. Thus the war, which began with a mass migration, ended in defeat and mass suicide.