piece (advisor or elephant), the enemy chariot or defensive piece might be able to capture the horse, which removes the cannon’s platform at the same time. Otherwise, capturing either checking piece is insufficient to remove the threat, unless the general makes the capture. Unique to xiangqi is a triple check, which arises in four combinations. In the first case of a cannon, a chariot or soldier, and a horse, the horse moves to give check, uncovering a double check from the chariot and the cannon. In the second, rarer case of a chariot or soldier and two horses, the chariot moves to give check, uncovering a double check from the two horses. In the third case of two cannons and two horses, one cannon may uncover a double check from the horses and act as a screen for the other cannon. Finally, a chariot or soldier can move to give check, uncovering a check from a horse while acting as a platform for a cannon to give another check. Quadruple check is also possible, arising with two horses, a chariot, and a cannon. Triple and quadruple check cannot be blocked or met by captures (again, unless the general makes the capture). Usually, soldiers do not support each other until the endgame, because from the initial position it takes a minimum of five moves of a soldier to allow mutual protection between two of them, and they are often prone to capture by other pieces. Soldiers, horses, cannons and chariots can form up formations that protect each other. However, lining up chariots must be done with caution, as this risks losing one chariot to an enemy's inferior piece. Horses that support each other are called Linked Horses(Chinese: 連環馬), which is a relatively safe formation of the horses, though it can still be threatened with a soldier, a chariot plus another minor piece, or a piece blocking one of the horses thus making the protection one-sided. It is common to use cannons independently to control particular ranks and files. Using a cannon to control the middle file is often considered vital strategy, because it pins pieces such as the advisors and elephants. The two files adjacent to the middle file are also considered important and horses and chariots can be used to push for checkmate there. Since the general is usually safest in his original position before the endgame phase, attacking the