You put your troops in squares and send them out in formation against the enemy formation. The battle is automatic. Each fomation you create has a limit though, about 1000 or 500 , your types of troops (Human, undead, etc ) and their quipment have a number that combine and make up the total sum which must be lower or equal the formation limit . You can buy a bundle and in each have a variry of equipment. I remember that weapon is vary and units too. Spear, Musket, Short bow, Long bow, Staff........Some special rings allow the wearer to summon undead troops when killed or reduce cast time and you cam have siege engine units too
Oh and you can test your formation against your friend or team up with them ( i think you use the formation with the limit of 500 ) to fight againt a special stage