Attacks that get rid of armor are considered to be Armor-Breaking. You may only choose to perform an Armor-Breaking attack if the monster still has at least one armor left . The amount of armor broken is known as attack power.

Any Armor the monster has must be broken before you can inflict any Wounds, unless noted otherwise. Move the token towards the 0 on the Monster’s Armor resource bar one space for each Armor broken. Until the Armor resource bar reaches “0” — you may not inflict Wounds through Weapon Attacks and Actions, unless specifically noted otherwise.