text: The Second Punic War broke out in 218 when Hannibal took control of the Greek city and Roman ally, Saguntum (in Spain). Rome thought it would be easy to defeat Hannibal, but Hannibal, leaving 20,000 troops with his brother Hasdrubal, went further north on the Rhone River than the Romans expected and crossed the river with his elephants on flotation devices. \n\nHannibal reached the Po Valley with less than half his men. He had also encountered unexpected resistance from local tribes, although he did manage to recruit Gauls. This meant he had 30,000 troops by the time he met the Romans in battle. \n\nHannibal won battles in Trebia and at Lake Trasimene, and then continued through the Apennine Mountains. With troops from Gaul and Spain on his side, Hannibal won another battle, against Lucius Aemilius, in which the Romans lost thousands of troops, including their leader. The historian Polybius describes the both sides of this, the Battle of Cannae, as gallant, and says of the losses:\n--\nHannibal's army in Iberia reportedly totaled 90,000 infantry and 12,000 cavalry, although those figures probably include Hasdrubal's forces as well as Hannibal's. The expeditionary force would still number as many as 75,000 foot soldiers and 9,000 horsemen. His army also had an unknown number of war elephants. \n\nAfter completing his overland journey, Hannibal descended from the foothills into northern Italy. He had arrived, however, accompanied by only half the forces he had started with, and only a few elephants. In total, Hannibal had lost as many as 20,000 men and all but three of his war elephants