Another new rule is the addition of "hidden armies", which are reinforcements that a player hides in a location of their choosing at the beginning of the game. They can be in any location, including an opponent's territory (except their own or an opponent's capital), which makes them very useful for launching a surprise attack. Hidden armies can only be withdrawn at the beginning of a players' turn and the player must have control of the territory at the start of their turn. Their power, when revealed, is based on the number of reinforcements cards that have already been played.