In short: although archangels are one unit faster than archdevils, the battle took place on lava, and the enemy attacked first. If I had gone first, the battle would have been much "more fun" for me. Believe it or not, it's up to you, but Inferno, which managed to gather a "decent" army, especially archdevils and sultan ifrits, is a formidable force!
The gates were destroyed on the 2nd turn, so the battle was a "head-on" clash.
I won this battle, and even resurrected all the fallen, but the attacking demon had almost no mana left: I captured his last city, and he didn't waste time refueling (which was a mistake!). Otherwise, things would have been much worse for me.
(Василь Симоненко. Люди – прекрасні)