Answer:
Because some people haven't gotten the technological development they require to fight against the other side
Step-by-step explanation:
The reason I said this was if they don't have the technological development like new guns and weapons and stuff like that, then they most likely wouldn't be very good at fighting. Like say 2021 America fought against 1832 Mexico. Obviously, America would win the fight, because they have the advantage of who has the most power, as well as defense, because they have the development they need.