I sent scouts to a level 7 grassland, from which they returned with a report saying that there are 1600 warriors, 400 pike-men and 350 swordsmen.
I used the Rally Spot to do an exercise to make sure that I don't lose a single archer in the battle.
I sent 2000 archers, which is way more than the minimum needed to win.

I LOST all of them, where the Rally Spot said I will lose none.
This is an astonishing 100% error margin!!!!!!!!!!!!!!!!!!!!
I had a war horn applied too.

My military tradition level is 8.
My archery level is 8.
My medicine level is 8.
My iron working level is 8.
My metal casting level is 8.
My hero's attack is 70.

By the way, I attacked the same valley with the same number of archers, but with a hero with attack 86, and had no losses.

Nabonassar