World history question that came to mind...

[revelarts]

Here's a World history question that came to my mind as I look at some the the threads here... new & old.

I'm not sure of the answer(s), at least in the way the question came to my mind.

the question is this.
How many empires fell via majors wars with enemies vs general slow collapse/decline?

And when empires fall, what major changes happen to the lifestyles of the people in those empires?

Trying to piece answers together in my head I don't have enough info for a good picture.
Outside of the major changes for those elites in leadership.

Off hand it seems "revolutions" are more regularly traumatic for the people in empires than being conquered, or collapse.
but again, my world history education is to sketchy here.