Kotobuki, the 611-Move Tsume Shogi, and the Longest Problems Since

The last problem in Ito Kanju’s Shogi Zuko, number 100, is called Kotobuki (寿). It mates in 611 moves.

Japanese Wikipedia’s entry on tsume shogi calls problems of up to 17 moves short, 19 to 49 moves medium, and 51 moves or more long. It adds that people draw the lines differently. By that scale, Kotobuki is more than ten times the threshold for a long problem.

How Shogi Zuko came to be presented to the shogunate in 1755 is in A History of Tsume Shogi. This post looks at how 611 moves are put together, and how the record was later broken.

The last three problems of Shogi Zuko

According to Japanese Wikipedia’s entry on Shogi Zuko, its 100 problems range from 9 moves (number 50) to 611 moves (number 100). The last three, number 98 “Bare King”, number 99 “Smoke Mate” and number 100 Kotobuki, are called the “divine games” for their beauty.

Ending a collection with one long problem was not Kanju’s idea alone. Japanese Wikipedia’s entry on ryu-oi (in Japanese) notes that number 100 of Shogi Muso, by his elder brother, the third Ito Sokan, is also a long dragon chase: “The Great Maze”, 163 moves.

Following Kotobuki without a diagram

Japanese Wikipedia’s entry on Kotobuki (in Japanese) explains the 611 moves as a combination of three devices.

The first is ryu-oi, the dragon chase. The dragon is a promoted rook. When it gives check from the square right next to the king, the king can only step to the diagonal square on the far side, and the dragon follows it diagonally, one square at a time. The wider the area the chase covers, the longer the solution. In Kotobuki the dragon chases the king around the whole board.

The second is a change of pieces in hand. Through repeated interpositions and sacrifices, the position on the board stays exactly the same while the attacker’s pieces in hand change. At the start, the attacker holds four pawns. One lap of the chase takes 42 moves, and after four laps the four pawns have become four knights.

The third is removing a piece. The board looks almost the same as before, except that one piece has disappeared. In Kotobuki, the defender’s tokin (promoted pawns) are made to capture a knight, and each time one of them is removed. When three tokin are gone, the solution enters its last stage.

All this travel has a purpose. The entry says the main theme is clearing a double pawn on the 1-file. From early on, there are moments when the attacker would like to drop a pawn on the 1-file, but there is already an attacking pawn on that file, so the drop would be an illegal double pawn. After the chases, exchanges and removals, that pawn finally disappears and a pawn can be dropped on 1-9. A few moves later, the dragon’s move to 3-9, move 611, gives mate.

A record that stood for 200 years

Six hundred and eleven moves was astonishing for its time. According to the same entry, Kotobuki held the record for the longest tsume shogi for about 200 years, until 1955.

The work that broke it was 新扇詰 (Shin Ogizume) by 奥薗幸雄. Japanese Wikipedia’s entry on Shin Ogizume (in Japanese) says it appeared in the New Year 1955 issue of the magazine Kindai Shogi and mates in 873 moves. It uses the same devices as Kotobuki: the dragon chase, the change of pieces in hand and the removal of pieces. A longer chase route and more round trips took it past Kotobuki.

The later records also appear in the All Japan Tsume Shogi Federation’s history of the Kanju Prize (in Japanese), the prize named after Kanju. For 1982, it records Meta Shinsekai (メタ新世界) by 山本昭一, 941 moves, which set a new record for length and won every vote for the prize.

The long-problem prize for 1986 went to Microcosmos (ミクロコスモス) by 橋本孝治. It beat the record by more than 500 moves: 1,519 moves when published, later reworked to 1,525. The same page says it still holds the record.

The long-problem prize for 2006 went to 新桃花源 by 添川公司, 1,205 moves. It became the second longest problem ever, and the first to pass 1,000 moves since Microcosmos.

The 1,525 moves of Microcosmos

According to Japanese Wikipedia’s entry on Microcosmos (in Japanese), it first appeared in the June 1986 issue of the magazine Tsume Shogi Paradise as a 1,519-move problem. In 1995 the composer published an improved version in the book 『詰将棋探検隊』, six moves longer, at 1,525 moves.

At the center of the 1,525 moves is the uma-nokogiri, the “horse saw”. The horse is a promoted bishop, and in this device it moves in a zigzag like the teeth of a saw. In Microcosmos the horse travels diagonally from 9-9 to 8-8, 7-7 and 6-6, and each of those one-square steps takes more than 300 moves.

To move the horse one square, pieces on the board are captured and then dropped by the defender elsewhere as interpositions, so that pieces change places. The change of pieces in hand from Kotobuki is used too, turning pawns or lances into knights. To lead the king where it is needed, the problem uses a device called chie-no-wa, “the puzzle ring”, which repeats a cycle of moves while changing the position a little each time. The entry adds that dividing the board and giving each device its own area is thought to be one reason the work succeeded.

“Beyond Kotobuki”

From the last years of the Showa era, which ended in 1989, into the Heisei era, long problems appeared one after another. The Kotobuki entry says that by 2006 Kotobuki was no longer among the ten longest.

Its name is still in use. The same entry says the phrase 寿超え, “beyond Kotobuki”, is sometimes used for problems of 611 moves or more, and that it serves as a mark for long problems and a goal for composers. Kanju’s name also lives on in the Kanju Prize, covered in Practical vs Composed Tsume Shogi.

How to keep a line of 7 or 9 moves in your head is in Reading 7-Move and 9-Move Tsume Shogi Without Getting Lost.

Solving tsume shogi in Shogi365

Shogi365 contains tsume shogi from mate in 3 to mate in 9, with 1,000 problems for each length, 4,000 in total. You choose by length.

You solve by playing on the board yourself. Any check, right or wrong, can be played, and the defender replies automatically. If you don’t mate within the move count, the attempt fails, and you can retry up to three times. After solving, the Review button steps through the line from the start position one move at a time.

All problems are free to solve. The app shows ads, and a one-time Remove Ads purchase turns them off. How to use the app is in Getting Started with Shogi365.