The units in your armies can be used to defend your own kingdom from attack, or to attack enemy kingdoms. A balanced army (using different types of units) will often prove to be more successful in combat, as some units attack at greater speed, whilst some units attack with far more strength.

Units: Slavers
To steal workers from an enemy kingdom you must use a slaver type unit. These units are vulnerable to enemy attacks, and have no means to engage the enemy. However, once a battle is over, the slavers may steal enemy workers, and they will become yours. Once a slaver has taken an enemy worker, it will have fulfilled its role and will leave your army, so it is nescessary to regularly train groups of slavers.