or tsume (詰め) is the Japanese term for a shogi miniature problem in which the goal is to checkmate the opponent's king. Tsume problems usually present a situation that might occur in a shogi game (although unrealistic artistic tsume shogi exists), and the solver must find out how to achieve checkmate. It is similar to a mate-in-n chess problem.
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.)
Tsume shogi problems are strictly forced mate problems with constant checks. They assume that the player is in brinkmate and that they will lose unless they can force a mate sequence with a check on every move. The situation simulates real shogi games in which the endgame is essentially a mutual mating race.
Note that the concept of stalemate as in western chess does not exist in shogi as it essentially does not occur.
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 tsume shogi.
The attacking side is ; meaning, he plays first. The attacking side's king is usually not present on the board. If it is, it is called a sōgyoku tsume shōgi (双玉詰将棋) problem. All of the attacking side's moves must be checks. White (the defender, or the side with the king) must move in such a way to delay checkmate as long as possible. So a mate earlier than the given moves is called an earlier mate. White has in hand all pieces not in the board or in the attacking side's hand, not counting the other king. White can drop any piece in hand to delay or prevent checkmate. Black cannot make a mate line longer than the given. So, he cannot extend a mate in 65 puzzle to a mate in 225.
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 tsume shogi prize in the shogi world is the "Kanju Prize".
Entering king
As a practical matter, when an opponent's king has entered a player's own territory, the opponent's king is often very difficult to mate given the forward attacking nature of most shogi pieces. This state is referred to as entering king (入玉 nyū gyoku). If both players' kings are in entering king states, the game becomes more likely to result in an impasse. (See Shogi § Impasse rule.)
Tactics
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 ("buttocks-gold") is gold position directly behind the king, and 腹金 harakin ("belly-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 a 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 (62, 42) leaving two escape routes for the king unless there is a knight behind the defender.