Order of battle rule 13.2.2 state that a player can determine to engage some but not all of the corps he has in a contested area. Battle Resolution rule 13.3.1 states each sides battle strength is the sum of all engaged corps including the army leader. My question is that true even if the player chose not to engage the army leader?
As I understand, you must engage your army leader. Otherwise you wouldn't be able to engage in a battle.
I'm not 100% sure though..