Quote Originally Posted by Caerfanan
Hi, Err, do you know what that would mean for a 5 atk 0 def Gallowglass for instance? Would they turn 0 atk, 5 def, or is it something else? Or for a -1 atk and 4 def unit?
(you seem to be quite the modder according to the other threads so I guess that you know a lot about the game's mechanics?)
It is -1 from attack and +1 to defence. So Gallo would become 4 atk 1 def. But don't do it! They need to either wedge into a strong spear unit or hit someone in the flank/rear and disperse among them on impact. Having them on hold formation will not allow them to do that.

Everything I know about the game mechanics I learned from here. Frogbeastegg's guide is very nice. Some other thread listing useful info also about bonuses and such.