Did the Roman Republic owe its success more to its form of government or to its army?

Both were Rome's strong points. Although they suffered plenty of defeats, they averaged out as winners, and were so able to continue expanding the territory they controlled and the revenue they harvested. It was government in which they particularly Excelled. Their system was to either use the existing local government or install a better type, but leave the locals to rule with military support from a Roman provincial governor; alternatively via a client king beholden to Rome, also with support from the Roman military nearby. Whatever the system, it meant that the country was ruled by its natural system of rule, and the local rulership took the responsibility and odium for controlling the populace and for taxes.