You also have some freedom to build your army. While it doesn't seem much at the start - you can choose from three types of infantry, two types of cavalry, and an artillery piece - your ability to only take four units makes for some serious mixing-and-matching. Plus, there's the choice of armaments. Is it muskets for everyone, or are you feeling pikey-and-shotty? Maybe you want bows? Sure, they allow targets much better saves, but you can shoot more than once a turn!
