One of Scipio's first major battles in Spain, this siege is described by Appian in his Iberica at 5.25-28.
Now this Hasdrubal ordered all the remaining Carthaginian forces in Spain to be collected at the city of Carmone to fight Scipio with their united strength. Hither came a great number of Spaniards under the lead of Mago, and of Numidians under Masinissa. Hasdrubal had the infantry in a fortified camp, Masinissa and Mago, who commanded the cavalry, bivouacking in front of it. Scipio divided his own horse so that Lælius should attack Mago while he himself should be opposed to Masinissa. This fight was for some time doubtful and severe to Scipio, since the Numidians discharged their darts at his men, then suddenly retreated, and then wheeled and returned to the charge. But when Scipio ordered his men to hurl their javelins and then pursue without intermission, the Numidians, having no chance to turn around, retreated to their camp. Here Scipio desisted from the pursuit and encamped in a strong position, which he had chosen, about ten stades from the enemy. The total strength of the enemy was 70,000 foot, 5000 horse, and thirty-six elephants. That of Scipio was not one-third of the number. For some time, therefore, he hesitated and did not venture a fight, except some light skirmishes. When his supplies began to fail and hunger attacked his army, Scipio considered that it would be base to retreat. Accordingly he sacrificed, and bringing the soldiers to an audience immediately after the sacrifice, and putting on again the look and aspect of one inspired, he said that the deity had appeared to him in the customary way and told him to attack the enemy, and had assured him that it was better to trust in heaven than in the size of his army because his former victories were gained by divine favor rather than by numerical strength. In order to inspire confidence in his words he commanded the priests to bring the entrails into the assembly. While he was speaking he saw some birds flying overhead with great swiftness and clamor. Looking up he pointed them out and exclaimed this was a sign of victory which the gods had sent him. He followed their movement, gazing at them and crying out like one possessed. The whole army, as it saw him turning hither and thither, imitated his actions, and all were fired with the idea of certain victory. When he had everything as he wished he did not hesitate, nor permit their ardor to cool, but still as one inspired exclaimed: "These signs tell us that we must fight at once." When they had taken their food he ordered them to arm themselves, and led them against the enemy, who were not expecting them, giving the command of the horse to Silanus and of the foot to Lælius and Marcius. Hasdrubal, Mago, and Masinissa, when Scipio was coming upon them unawares, being only ten stades distant, and their soldiers not having taken their food, drew up their forces in haste, amid confusion and tumult. Battle being joined with both cavalry and infantry, the Roman horse prevailed over the enemy by the same tactics as before, by giving no respite to the Numidians, thus making their darts of no effect by reason of their nearness. The infantry were severely pressed by the great numbers of the Africans and were worsted by them all day long, nor could Scipio stem the tide of battle, although he was everywhere cheering them on. Finally, giving his horse in charge of a boy, and snatching a shield from a soldier, he dashed alone into the space between the two armies, shouting: "Romans, rescue your Scipio in his peril."3 Then those who were near seeing, and those who were distant hearing, what danger he was in, and all being in like manner moved by a sense of shame and fear for their general's safety, charged furiously upon the enemy, uttering loud cries. The Africans were unable to resist this charge. They gave way, as their strength was failing for lack of food, of which they had had none all day. Then, for a short space of time, there was a terrific slaughter. Such was the result to Scipio of the battle of Carmone, although it had been for a long time doubtful. The Roman loss was 800; that of the enemy 15,000. After this engagement the enemy retreated with all speed, and Scipio followed dealing blows and doing damage whenever he could overtake them. After they had occupied a stronghold, where there was plenty of food and water, and where nothing could be done but lay siege to them, Scipio was called away on other business. He left Silanus to carry onthe siege while he went into other parts of Spain and subdued them. The Africans who were besieged by Silanus deserted their position and retreated again until they came to the straits and passed on to Gades. Silanus, having done them all the harm he could, rejoined Scipio at New Carthage. In the meantime Hasdrubal, the son of Hamilcar, who was still collecting troops along the Northern ocean, was called by his brother Hannibal to march in all haste to Italy. In order to deceive Scipio he moved along the northern coast, and passed over the Pyrenees into Gaul with the Celtiberian mercenaries whom he had enlisted. In this way he was hastening into Italy without the knowledge of the Italians.