Complex sentence: When in 218 BC, war broke out between Carthage and Rome, Syphax was initially sympathetic to the Romans and in 213 BC, he concluded an alliance with the Romans and they sent military advisers to help Syphax train his troops.
Split into simpler sentences: When in 218 BC, war broke out between Carthage and Rome, Syphax was initially sympathetic to the Romans. In 213 BC, he concluded an alliance with the Romans and they sent military advisers to help Syphax train his troops.