How does "auto-resolve" work in battles?

Solution 1:

Should you have more than one general in your army it's quite possible to lose them in an evenly matched battle. With a singular general you may lose a larger portion of their squad, but otherwise it's highly unlikely to lose the general themself.

If you heavily outnumber the enemy you'll generally encounter less losses with an autoresolve than a manually controlled battle, even if it were on the easiest difficulty setting.

In an scenario where you yourself are outnumbered you're better off manually controlling your troops rather than autocompleting it, auto = zero chance of success in such a case, whereas with manual control it's still possible to achieve victory.

The autoresolve purely deals with numbers, not terrain or the like, defending forces are given a numbered boost if in fortifications, and attacking forces counterboosts for siege weapons. A slight variance in outcomes from a random number generator for each smaller outcome of individual troops makes some small differences but that's all.

Also the level of difficulty set for the enemy ai can make a large difference, a singular ranged troop behind fortifications can fight off a full army to a timeout victory on the lowest difficulty, whereas on higher difficulty or with an autoresolve that's not possible.