There under 4 categories of Units (Army, Air Force, Navy and Special) that are used when attacking or defending against militaries of other players. Each category has specific Class of units. In a Battle, best in each Class of Units in every category is used.
Example: In Ground inventory category, Machine gunner is best for defense defence but Scout sniper is best for the attack. You need to deploy both if you want both attack and defense defence to be strong. Follow the same pattern in all the categories and you will be a stronger player. Some units are 'Destruct Units' that get destroyed during wars. More powerful Units become available as you go up in level. Some Units called Pillage cannot be bought and can only be gained by doing Ops. ===Army=== ===Air Force=== ===Navy=== ===Special===