Disease, Armor, Guns, and Horses
Answer:
...
Explanation:
You could compare how children aren't aloud to work anymore and how child labor is illegal compared to in history it was acceptable.
I'm not sure bc the question was kinda vague but i hope i helped :)
Since Roman was expanding and it didn't have control of their lands and couldn't govern most of it. It kept expanding until the western part of Roman was conquered by Barbarians.