Wednesday, February 18, 2015

Tsume: Japanese Chess Mating Puzzles

Tsume shogi, or just tsume for short, are Japanese chess mating puzzles. I just created a browsable tsume shogi database, so I thought it might be a good idea to explain tsume rules, background, and their benefits.

Imagine a situation where you are playing a much more skilled shogi player than yourself. You are losing. Your opponent will place you in checkmate in one move. You are desperate. Your only chance is to check your opponent, and keep him in check until you have a checkmate. Otherwise, you will lose the shogi game.

One-move shogi tsume
This is a one-move tsume of my own creation.
See if you can spot the checkmate.



Anyone who has lost a game of shogi has been in this situation. Tsume were designed specifically to teach this endgame skill. Practicing tsume helps immensely with your shogi endgame.

Tsume study is not only useful for people playing against superior opponents. Skilled players should spend a lot of time studying tsume, too. Imagine how aweful it is to be one move from victory against an inferior opponent, and losing because you allowed a tsume to form on your side of the board!

Don't forget to examine your own king for possible tsume, while attacking your opponent.

Tsume Rules

The rules for tsume are similar to regular shogi. Obviously, tsume is for one player, rather than shogi in which two players play. You always play up the board as Black in tsume shogi. Black must place White in check on every move, or lose instantly. White is considered to have every piece in hand (except Black's king) unless the pieces are in Black's hand or on the board.

In tsume, futile interpositions are not allowed. That means, if checkmate will happen to the king on its current square, with the same piece checkmating the king (a lance, bishop, or a rook), a drop to block the checkmate is not allowed. In a real game, you would be expected to resign at this point, rather than act with poor sportsmanship and make desperate drops to no effect.

In tsume, black must checkmate as quickly as possible. White (with the exception of futile interpositions) must avoid checkmate as long as possible.

Tsume often only show the opposing king. Certain types of tsume (called double-king problems or sougyokumondai) show both kings. In these tsume you must avoid allowing your own king to be captured while capturing your opponent's king.

Tsume History and Trivia

The oldest existing collection of tsume puzzles was written by Ohashi Sokei in 1602. That means the art of tsume is over 400 years old! Sokei's collection of tsume, entitled Shogizobutsu, is still studied by shogi enthusiasts.

In Japan, you can find many books dedicated to tsume puzzles. The most popular with beginners are one, three, and five-move tsume books. More advanced tsume books with seven-move tsume, nine-move tsume, or even more complex tsume are also available. The English tsume book I wrote, contains tsume for beginners and more advanced shogi enthusiasts. (Yeah. I couldn't help sticking in a shameless plug for my own tsume book.)

At some point you're going ask, "What is the longest tsume?" Believe it or not, the longest tsume puzzle is 1525 moves long. It even has it's own name, ... Microcosmos. As far as I know, it has only been solved by computers, but I'm sure a real shogi master could pull off solving it, given enough spare time.

Hints for Solving Tsume

A well designed tsume always results in all your pieces in hand being dropped during the solution. If you capture a piece or start with a piece in hand, expect to drop it on the board at some point. If you solve the tsume, and still have pieces in hand, double-check your solution. There may have been an escape that the king could have taken that you missed.

Don't forget that the pawn cannot checkmate—only check—the king when dropped. Some tsume have two solutions, one with an illegal pawn drop checkmate as a trap. Find the solution without the illegal pawn drop, and you have solved the tsume.

Look for unexpected moves and sacrifices. Some of the best tsume involve giving up a rook or bishop to arrange the enemy's pieces in just the right way to allow a checkmate.

Watch for moves that open up two lines of attack on the enemy king. Often, you will examine a board and be convinced that any move you make to place the king in check will result in that piece being captured. However, if you look at the shogi pieces carefully, you will realize that a range attacking piece, meaning the lance, bishop, or rook, also attack the king once the moved piece is out of their line-of-sight. This is very common in difficult one-move tsume.

In very rare, and difficult tsume, White must drop specific pieces from its hand in order to avoid checkmate later on. I've only run into one of those, and created one myself, but they're out there.

Another common trick to use while solving tsume is to layout the tsume on a real shogi board. That way you can experiment with moving pieces around without visualizing all the moves in your head. Eventually, you won't need this trick, but it is handy for beginners.

Summary

Tsume shogi puzzles are fun. Even if you don't have time for a full game of shogi, cracking open a tsume book or solving a tsume online only takes a few minutes, and doesn't require much of a commitment. At first, you may only feel confident enough to solve one-move tsume, but over time you will graduate to three, five and seven-move tsume. The best benefit of all is that your shogi endgame will improve immensely.

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