Whether to excel in battle or not is not always proportional to the number of soldiers.
Whether it's proportional or not depends on tactics, that is, yourself.
(I.e., if you have tactics, whether to excel in battle or not is proportional to the number of soldiers.)
It says "比例するかそうでないか depends on tactics/yourself", not "whether 戦に勝る or not depends on tactics/yourself".