Final answer:
Hannibal marched over the Alps to inspire Rome's allies to defect and to avoid Rome's superior naval forces. His strategy involved surprise and demonstrating the determination of Carthage, but ultimately, limited alliances and lack of siege equipment hindered his campaign, which ended with his recall to defend against a Roman offensive in Africa.
Step-by-step explanation:
Hannibal chose to march his army across land and over the Alps into Italy during the Second Punic War rather than sail directly to Rome because he sought to demonstrate his strength and inspire Rome's allies to defect.
While a sea voyage might seem faster, Hannibal's strategy involved engaging Roman allies in the Italian peninsula, leveraging the element of surprise and hoping that the display of commitment and power would cause a political shift. His passage through the Alps was deemed impossible by the Romans, and it showed his military genius and the determination of the Carthaginian army.
Moreover, Rome's naval supremacy made a direct maritime attack risky, while their land defenses were comparatively weaker. Hannibal's military tactics during his campaign were impressive; he managed to win multiple battles, including the infamous Battle of Cannae, using clever maneuvers and strategies.
Unfortunately, Hannibal was unable to secure lasting alliances with the Italian city-states, and he lacked the siege engines necessary for assaulting Rome. As the war dragged on, his army became isolated and his situation worsened, especially after the Roman general Scipio began an offensive in North Africa, forcing Hannibal to return home to defend Carthage.