https://youtu.be/h9jyBL6f4gk?si=yCom0KdAiZFjHZhj&t=66

Interesting thing is, he mentions slaves weren't allowed to serve in the military. (But I suspect they were "used" by the military a lot. I mean... why wouldn't you use them?)

Another interesting bit is there were so many slaves romans feared they would revolt. Even plans for a slave uniform were scrapped so the slaves can't easily see their real numbers.