Yagura (castle)
The Yagura castle (矢倉囲い yagura gakoi) is a castle that appears most frequently in Double Static Rook and Double Ranging Rook openings. The basic shape of the Yagura castle consists of a silver on 77 and a gold on 78.
Strategy
Strengths and Weaknesses
In shogi, every castle has strengths and weaknesses, and the Yagura castle is no exception to this rule. Understanding the Yagura's strengths and weaknesses makes it easier to find the best measures and countermeasures to use, playing with or against a Yagura castle.
The Yagura castle is strong at defending attacks against the king's head, and weak against defending attacks from the flank. For this reason, the Yagura castle is well suited for the Double Static Rook and Double Ranging Rook openings in which it most frequently appears. Nevertheless, the Yagura castle can also be used in opposition games. For example, Yasuharu Oyama once successfully employed a Static Rook Yagura castle against Hatasu Ito's Ranging Rook Anaguma castle.[1] As Oyama demonstrated in this game, against Ranging Rook strategies, the Yagura castle can be developed into a King's Head Vanguard Pawn formation to emphasize the thickness at the head of the castle.
An advantage of the Yagura castle is that the king's position on 88 is covered by the gold on 78 and the silver on 77. Consequently, it is difficult to chase the king out of a Yagura castle with consecutive checks in the endgame. In contrast, the Mino castle does not have this advantage.
The 76 square is a weak point of the Yagura castle. If the silver is attacked with an opponent's pawn on 76, the Yagura shape will be broken and not easily repaired.
The edge is a weak point of the Yagura castle. In most variations of the Yagura castle, the edge is defended by only a lance and a knight. For this reason, the Yagura castle is vulnerable to edge attacks.
King Position
The characteristics of the Yagura castle can change depending on the king position.
When the king is castled to 79, the king is vulnerable to checks from bishops along the diagonal from 79 to 13, and from rooks on the back rank. Nevertheless, the 79 square can be safer from attacks against the head of the Yagura castle. Shintaro Saito used this property to successfully initiate an attack from the head of his Yagura castle against Seiya Kondo's Right King castle.[2] Although it is risky and often ill-advised to use a castle for attack, Saito benefitted from the fact that his king, on the 79 square, was far from the battlefield.
When the king is castled to 88, the king is less vulnerable to attacks from the flank. On the other hand, edge attacks and attacks against the head of the Yagura castle become more severe when the king is castled to 88. In addition, the king is in the direct line of fire of the opponent's bishop on the long diagonal. In the third game of the 2023 Meijin title match, Akira Watanabe castled his king to 88 on move 37, a dubious and provocative move which induced Sota Fujii to attack on the long diagonal. Although the AI evaluation was in Fujii's favor, Watanabe gained the upper hand and won the game after extreme complications in the middlegame and endgame, containing multiple consecutive threatmate-removing threatmates and a critical variation leading to an illegal perpetual check.[3]