Leadership Ability: This rates the character’s capability to give orders and have them obeyed. Leadership ability determines the number of activation points (AP) that a commander receives. It also determines the number of divisions a general may have in his army. Leadership ability ranges from 1 to 8.
So I searched for all other strings of Leadership Ability on my PDF version of ACKS Domains at War: Battles. I cannot find what defines what the leadership ability is composed of. I would presume it is some combination of ability and proficiency...or is this one of those rules entirely up to the GM to determine.