Complex sentence: The Second Punic War (218--201) started over a dispute concerning Saguntum (near modern Valencia) in Hispania, from whence Hannibal Barca set out, leading his armies over the Alps into Italy.
Split into simpler sentences: The Second Punic War (218--201) started over a dispute concerning Saguntum (near modern Valencia) in Hispania. It was from there at Hannibal Barca set out, leading his armies over the Alps into Italy.