YouTuber Historia Civilis aptly showcases the evolution of Roman battle tactics. And while the content treads a simplistic (though nifty) overview, we can get the core idea behind the Roman military system and how its adaptability set it apart from most of the ‘stagnant’ armies of the ancient world. Definitely worth the watch.

http://www.realmofhistory.com/2016/05/10/animated-evolution-roman-battle-tactics/