Ok, the AMOUNT of exp units gain is unclear but all units gain exp for dealing damage, for example: if 100 tanks (of any kind) goes up against one spam only ONE of the tanks will get a tiny amount of exp. Now imagine there is an extreamly big battle that lasts 6 rounds, the surviving units would have gained a massive amount of exp.
wiki.battledawn.com wrote:
Units get experience by winning battles in colonies,outposts or relics.Each unit that accumulate experience will get stronger,so if before a EMP Trooper was defeated by a Martian Marksmen,with some experience the EMP trooper may win the battle against the M.Marksmen
I hope that answers your question