Castle (shogi)

In shogi, castles (囲い kakoi) are strong defensive configurations of pieces that protect the king (玉). Usually the pieces involved are golds (金), silvers (銀), and pawns (歩). Typically, they also require moving the king from its starting position – often to the left or right side of the board.

In contrast to the special castling move in western chess, shogi castles involving making multiple individual moves with more than one piece. The simplest castle involves two pieces and requires three moves, but it is more common to move at least three different pieces. For example, a simple Mino castle (美濃) requires moving the king, the rook (飛), a silver, and two golds for a total of six moves. Others such as the Static Rook Anaguma castle (居飛車穴熊) are more complex, which requires moving the king, a pawn, the bishop (角), a lance (香), a silver, and two golds for a total of twelve moves. Furthermore, there are piece development relations between castles. For instance, a basic Mino castle can be developed into a Silver Crown castle, a Gold Yagura castle can be developed into a Complete Yagura castle, a Boat castle into an Anaguma castle, a Gold Excelsior castle into a Left Yagura castle, and so on.

There are many types of castles and variations on those types which can be used, but it is important to understand which ones are useful in the current situation and how to compensate for their weak points.

The lack of a castle and with the king in its start position is known by the term sitting king (居玉 igyoku), which is typically regarded negatively. However, there are a few very early attack strategies that allow a sitting king.

Certain castles are generally paired with certain openings. For example, if White is playing a Ranging Rook opening like Fourth File Rook, then White often uses a Mino (or related) castle on their right side of the board. A Fourth File Rook opening can be met with Black playing a Static Rook opening, which may often lead to Black building a Static Rook Anaguma castle.

The Yagura or Fortress castle (矢倉囲い yaguragakoi) is considered by many to be the strongest defensive position in shogi in Double Static Rook games.

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Wikipedia