Well, when I thought of this, the main scenario is actually after a skirmish or a big battle. This might give the losing player which are forced to be on the defense a comeback chance, without the offensive side gaining too much upper-hand which might GG the game early. This might lengthen the game time (can be good or bad, personal preference), it's kinda bleak to just build army and win without exploring more features of the game. Besides, the offensive side might be suffering from troops with low HP (or stamina...waiting for implementation) which might decrease their effectiveness , but their troops have the experience accumulated and veteran level to maybe balance it out without suffering a clear disadvantage. (Maybe a small, slight vet bonus for professional soldiers as well?) Thus, the offensive side have the option to battle all out if he has the confidence to defeat fresh enemy troops or live to fight another day, giving the player a slight advantage by having more battle-hardened veterans. P.S : When a unit gain level, the immunity granted for it, is it intended or a bug? This might break the game, if intended to be immune, maybe make it unable to target or slight reduction in damage taken. ( I've seen some of my troops hitting them and die to other enemy units as a result )