This unexampled success appeared at length to mature the great political combination, for the sake of which Hannibal had come to Italy. He had, no doubt, based his plan primarily upon his army; but with accurate knowledge of the power opposed to him he designed that army to be merely the vanguard, in support of which the powers of the west and east were gradually to unite their forces, so as to prepare destruction for the proud city. That support however, which seemed the most secure, namely the sending of reinforcements from Spain, had been frustrated by the boldness and firmness of the Roman general sent thither, Gnaeus Scipio. After Hannibal's passage of the Rhone Scipio had sailed for Emporiae, and had made himself master first of the coast between the Pyrenees and the Ebro, and then, after conquering Hanno, of the interior also (536). In the following year (537) he had completely defeated the Carthaginian fleet at the mouth of the Ebro, and after his brother Publius, the brave defender of the valley of the Po, had joined him with a reinforcement of 8000 men, he had even crossed the Ebro, and advanced as far as Saguntum. Hasdrubal had indeed in the succeeding year (538), after obtaining reinforcements from Africa, made an attempt in accordance with his brother's orders to conduct an army over the Pyrenees; but the Scipios opposed his passage of the Ebro, and totally defeated him, nearly at the same time that Hannibal conquered at Cannae. The powerful tribe of the Celtiberians and numerous other Spanish tribes had joined the Scipios; they commanded the sea, the passes of the Pyrenees, and, by means of the trusty Massiliots, the Gallic coast also. Now therefore support to Hannibal was less than ever to be looked for from Spain.
On the part of Carthage as much had hitherto been done in support of her general in Italy as could be expected. Phoenician squadrons threatened the coasts of Italy and of the Roman islands and guarded Africa from a Roman landing, and there the matter ended. More substantial assistance was prevented not so much by the uncertainty as to where Hannibal was to be found and the want of a port of disembarkation in Italy, as by the fact that for many years the Spanish army had been accustomed to be self-sustaining, and above all by the murmurs of the peace party. Hannibal severely felt the consequences of this unpardonable inaction; in spite of all his saving of his money and of the soldiers whom he had brought with him, his chests were gradually emptied, the pay fell into arrear, and the ranks of his veterans began to thin. But now the news of the victory of Cannae reduced even the factious opposition at home to silence. The Carthaginian senate resolved to place at the disposal of the general considerable assistance in money and men, partly from Africa, partly from Spain, including 4000 Numidian horse and 40 elephants, and to prosecute the war with energy in Spain as well as in Italy.
The long-discussed offensive alliance between Carthage and Macedonia had been delayed, first by the sudden death of Antigonus, and then by the indecision of his successor Philip and the unseasonable war waged by him and his Hellenic allies against the Aetolians (534-537). It was only now, after the battle of Cannae, that Demetrius of Pharos found Philip disposed to listen to his proposal to cede to Macedonia his Illyrian possessions - which it was necessary, no doubt, to wrest in the first place from the Romans - and it was only now that the court of Pella came to terms with Carthage. Macedonia undertook to land an invading army on the east coast of Italy, in return for which she received an assurance that the Roman possessions in Epirus should be restored to her.