Castle

In shogi, a castle (囲い kakoi, literally "enclosure") is a defensive formation consisting of two to four connected generals that guard the king. There are a wide array of castles to choose from, and using a particular castle (or choosing not to castle) is a strategic decision that could make the difference between victory and defeat. The two main factors to consider are: the type of opening being played and the direction of the attack. In accordance with the proverb "Keep the king and rook separated", a player using a Swinging Rook strategy (where the rook moves to the left side of the board) will typically castle to the right, while a player using a Static Rook strategy (where the rook stays on the right side) will castle to the left. There are exceptions to this rule, as well as central castles. With the recent popularity of rapid attacks, it's not uncommon for even pro shogi players to forego castling entirely, using only a cursory defense as needed.