How did Scipio Africanus change his army’s formation at the Battle of Ilipa?

At the Battle of Ilipa, Scipio Africanus strategically altered his army's formation to ensure he was strong where the Carthaginian forces were weak.

After lulling the enemy commanders into a sense of routine through days of light skirmishing, Scipio changed his troop order on the day of the battle. He positioned his Roman veterans on the flanks to advance against the Carthaginian Iberian mercenaries, while his Spanish allies were placed in the center with orders to "refuse the centre." This meant the Spanish troops held the main body of the Carthaginian army in place without fully engaging, allowing Scipio's veterans—reinforced by cavalry and velites—to exert pressure on the flanks. This maneuver caused the Carthaginian flanks to collapse, leaving their center unable to respond effectively to the subsequent general advance.12