This brings up the other annoying point of having to always ensure sticker supplies are kept high, for fear of not being able to keep enemies at bay during fights. (cubed3.com)
To add more units, you'll need to capture cities (resources) and additional factories while keeping the enemy at bay. (playstationlifestyle.net)
Deploy a fearsome ground attack of swordsmen, knights, and donkey riders in order to protect your castle games, and if all else fails, call upon powerful spells to help keep the enemy at bay. (metacritic.com)