Tsumeshogi (詰将棋 or 詰め将棋, tsumeshōgi) or tsume (詰め) is the Japanese term for a shogi problem in which the goal is to checkmate the opponent's King. Tsume problems present a situation that might occur in a shogi game, and the solver must find out how to achieve checkmate. It is similar to a chess problem.
Contents
- Rules
- Purposes of tsume problems
- Shogi training
- As a work of art
- Mating with gold
- Mating and promotion
- Mating and unpromotion
- Fast checkmates
- Fastest shogi checkmate
- References
The term tsumi (詰み) means the state of checkmate itself. The verb form is tsumu (詰む) "to checkmate". (The related term tsumero 詰めろ refers to the slightly different concept of "threatmate". See: Hisshi.)
Note that the concept of stalemate as in western chess does not exist in shogi as it essentially does not occur. Thus, tsumeshogi problems are strictly mate problems.
Rules
Tsume problems have set rules for how they must be constructed and completed. If the solver breaks any of the rules, he has not solved the problem correctly. If the composer breaks any rules, he has not constructed a tsumeshogi.
Purposes of tsume problems
Tsume problems can be used to fulfill one of two tasks: to train in shogi strategy or to be created as a work of art.
Shogi training
Tsume problems are considered very good training for playing shogi. They teach not only how to effectively checkmate the king but also to predict moves and plan out a long series of moves before achieving a goal. There are many websites and books dedicated to tsume problems for this purpose.
As a work of art
Many shogi players for centuries have created tsume problems with long and deliberate mating lines as artwork. They might consist of the pieces making geometric shapes, a theme which is used throughout the problem, the removal of all pieces on the board (called a Smoke Mate), or a set number of moves. One of the most famous tsume artists is Kanju Itou, who in 1755 wrote Shogi Zukou (将棋図巧), a famous collection of artistic tsume problems. The main tsumeshogi prize in the shogi world is the "Kanju Prize".
Mating with gold
A common move in the endgame is to checkmate an opponent's king with gold drop when the position that the gold is dropped to is also defended by another piece.
Japanese has three terms for this depending on the position of the gold in relation to the king. A gold dropped directly in front of the king is 頭金 atamakin ("head-gold"). 尻金 shirikin ("bottom-gold") is gold position directly behind the king, and 腹金 harakin ("stomach-gold") is a gold placed on the side of the king.
Since many pieces (pawn, lance, knight, silver) can all promote to gold-like piece, checkmate by a gold is usual.
Because of the relative ease of mating with a gold compared to other pieces, it is often advantageous to keep an gold in hand during the endgame so that a mate with a dropped gold can be executed.
Mating and promotion
Since mate by gold is a fundamental checkmate tactic in shogi, it is common for pieces to promote into a gold to deliver checkmate.
For instance, a silver defended by a pawn can mate at the head of a king but only if the pawn is promoted. A silver protected by a pawn, lance or rook cannot attack the side squares (6b, 4b) leaving two escape routes for the king unless there is a knight behind the defender.
As another example, a knight may mate a king if promoted to a gold as well (as shown in the diagrams to the right). If the knight didn't promote here, then there would be no checkmate.
Mating and unpromotion
In other situations, staying unpromoted can lead to a mate while promoting does not result in mate. In the example, if the knight on 8e moves to 7c and does not promote, it attacks the king and delivers checkmate (since the horse is also attacking the b rank squares in front of the king). However, if the knight moved to 7c and promoted to the gold-like narikeima, then the promoted knight isn't attacking the king leaving White a chance to counterattack to avoid checkmate.
The same is true with the silver example to the right. If the silver promoted at 8c, then it would not be checkmate since a gold-like promoted silver cannot attack backwards diagonally.
Fast checkmates
Like the famous Scholar's mate in western chess, shogi has a well-known early mate sequence related to the joseki for Cheerful Central Rook vs Static Rook games. For example, if Black is playing Cheerful Central Rook, then if White deviates from the jouseki and blunders by creating a wall with their either of their silvers (S-6b or S-4b), then Black will give a double check with their rook and promoted bishop rendering an 11-move mate as follows:
Similar variants of this sequence are also possible. For example, Kitao (2011) offers the following position with these implied moves:
Fastest shogi checkmate
1. P-7f G-7b 2. Bx3c+ G-4b 3. +Bx4b K-6a 4. G*5b (tsume)