How were the romans so successful in conquering and holding such a vast territory?

- They placed Legions ( an army unit consist of thousands of men to guard each of their territories)

- They create code of law, and implemented a governmental system at their conquered territories

- They Acquired a lot of non Roman armies to help them in their cause

The main reasons why the Romans were so successful in conquering and holding such vast territories was the fact that they had very good general and generally they had avery good structure in their army which meant that their soldiers were always well equipped and supplied + trained in tactics which cannot be said for other barbarian nations at the time. 

The correct answer is c