Control of Syracuse does not by itself give the army freedom of action. A navy is required because the troops otherwise cannot leave Sicily, and the city is considered as a possible capital. Ports and ships must convert territorial possession into movement across the sea. Within the game scenario, Syracuse can become the base from which Carthage projects force toward Italy.
Chapter · 2:18:34-2:19:05
Why Syracuse needs a fleet to project power
After taking Syracuse, the army remains trapped on Sicily until naval transport exists, even if the city becomes a strong Carthaginian base.