Sennichite
Sennichite (千日手) or Repetition Draw is a rule in shogi stating that the game will end in a draw if the same position is repeated four times during a game.
Explanation
If the same game position occurs four times with the same player to move, either player loses if his or her moves during the repetition (sennichite) are all checks (perpetual check), otherwise the game is considered a draw. However, in Shogi a draw is not counted for. Players have to restart their game(s) until a winner is declared. This is a significant difference from western chess, in which a player can play specifically to obtain draws for gaining points. In Shogi there can be only one victorious through wins. When a draw situation in Shogi occurs, the players have to start a new game in which the players switch colours. The player who was white, becomes black and vice versa. Furthermore, depending on the tournament, players who have reached sennichite need to start and play their new game in the remainder of their allowed game time. This rule also contributes to making sennichite a rare occurrence. Repetition draws in shogi are also rare to achieve, since through the four iterations, every iteration needs contain the same positions. For two positions to be considered the same, even the pieces in hand must be the same as well as the positions on the board. Although rare among professional players, Repetition Draws are even rarer in amateur games.
History
Pre-1983 sennichite. The sennichite rule was previously defined by a sequence of moves (and not a position) that had three repetitions. The rule was changed to its current form in May 1983.
Historical sennichite. There was yet another repetition rule used historically by rule codifier Sōko Ōhashi who was the second Meijin from 1635 until his death in 1654: the player that started a repetition lost the game.[1]
Example
Watanabe vs Habu 2012
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Repetition Draw Watanabe vs Habu 2012 △ pieces in hand: 金2 歩1
▲ pieces in hand: 飛2 銀1 桂1 歩5 Position after 61. ... S*6f, 62. Px6f before Habu initiated the Repetition sequence.
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Repetition Draw Watanabe vs Habu 2012 △ pieces in hand: 金1 歩1
▲ pieces in hand: 飛2 銀1 桂1 歩5 62. ...G*8i
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Repetition Draws have historically been associated with the traditional Double Yagura opening (especially the Complete Yagura formation).[2] However, a surprising Repetition Draw occurred in the endgame of a game between Akira Watanabe (Black) and Yoshiharu Habu on October 3, 2012.[3] The opening was Third File Rook.
After the 121st move (= 61st move in western notation), White (Habu) found himself in a threatmate situation where Black (Watanabe) had a possible 9-move mate sequence of 62. R*8c Gx8c, 63. Sx8c+ Kx8c, 64. R*8b Kx7d, 65. N*6f K-6c (or K-6d), 66. G*5d [mate]. In order to prevent Black's future knight drop (N*6f), White dropped a silver to the 6f square (61. ...S*6f) forcing Black to capture it with his pawn (62. Px6f) leaving the 6f square occupied and unable to accept a knight drop.
After this, White found the Repetition sequence starting with 62. ...G*8i. Dropping the gold to the 8i square puts Black in his own threatmate situation as White is threatening the mate-in-one 63. ...Bx8h+ [mate] on his next move.
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Repetition Draw 2012 △ pieces in hand: 金1 歩1
▲ pieces in hand: 飛1 銀1 桂1 歩5 63. R*7h
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Repetition Draw 2012 △ pieces in hand: 金2 歩1
▲ pieces in hand: 飛1 銀1 桂1 歩5 63. ...Gx8h
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Therefore, Black defends the 8h square in the only way he can by dropping a rook to the seventh file (63. R*7h). He cannot remove White's gold with his own gold on 8h (63. Gx8i) since that gold is pinned by White's bishop on 7i.
White, then, trades his golds via the 8h square (63. ... Gx8h). This move is actually forced as Black is threatening to create a 3-move brinkmate sequence via 64. S*8b Gx8b, 65. Nx8b+. And, since White does not have any checkmate sequence available to him, after this, Black will have a mate-in-one with +N8c (or G*8c or R*8c). Thus, White must defend against the brinkmate by creating another threatmate against Black with 63. ...Gx8h. This threatens the 3-move mate sequence: 64. ...Gx7h, 65. K-9h B-8h+ [mate].
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Repetition Draw 2012 △ pieces in hand: 金2 歩1
▲ pieces in hand: 飛1 金1 銀1 桂1 歩5 64. Rx8h
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Repetition Draw 2012 △ pieces in hand: 金1 歩1
▲ pieces in hand: 飛1 金1 銀1 桂1 歩5 64. ...G*8i
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Black, of course, must defend against the threatmate by capturing White's gold with his rook (64. Rx8h).
After White's gold is removed, the board position is very similar to the position at after the 123rd move (the first diagram shown above). The only difference is that instead of Black having a gold on the 8h square Black has a rook on 8h. However, this is sufficiently similar to force Black into a Repetition sequence in that Black's rook like the previous gold cannot capture White's bishop on 7i and also is pinned by the same bishop. And, since White still has a gold available to drop, he drops a gold again to the 8i square (64. ...G*8i). This creates another threatmate (threatening again the same mate-in-one ...Bx8h+).
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Repetition Draw 2012 △ pieces in hand: 金1 歩1
▲ pieces in hand: 飛1 銀1 桂1 歩5 65. G*7h
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Repetition Draw 2012 △ pieces in hand: 飛1 金1 歩1
▲ pieces in hand: 飛1 銀1 桂1 歩5 65. ...Gx8h
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Black must again stop the threatmate by defending the 8h square – this time with a gold (65. G*7h).
Similarly, White captures the rook on 8h with their gold creating the same threatmate as above (65. ...Gx8h). It is here on the 130th move that the Repetition sequence technically starts.
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Repetition Draw 2012 △ pieces in hand: 飛1 金1 歩1
▲ pieces in hand: 飛1 銀1 桂1 歩5 66. Gx8h
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Repetition Draw 2012 △ pieces in hand: 飛1 金1 歩1
▲ pieces in hand: 飛1 銀1 桂1 歩5 71. ...Gx8h
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White must again remove the threatmate by capturing White's gold (66. Gx8h).
After these eight moves, we have a near identical position to the position after the 122nd move (62. Px6f). However, there is a small difference in that now White has a rook in hand instead of the two golds and Black has a gold in hand instead of two rooks. Thus, although very similar (and functionally the same in terms of game play), this is not a repetition of the board position at move 122 and why the actual Repetition sequence starts at move 130.
After 66. ...G*8i, 67. G*7h Gx8h, there is a second repeat of the position at move 130. After 68. Gx8h G*8i, 69. G*7h Gx8h, there is a third repetition. And, after 70. Gx8h G*8i, 71. G*7h Gx8h, White makes the fourth repetition leading to a Repetition Draw. After this, a new game was started with Habu playing Black and Watanabe playing White.
See also
- Threefold repetition (a similar rule in western chess)
- Perpetual check (a type of repetition in western chess, but illegal in shogi)
Notes
- ↑ Fairbairn (1986: 134, 136–138)
- ↑ Fairbairn, John (1981). "How to play the fortress opening part 1". Shogi (29): 4–6.
- ↑ http://live.shogi.or.jp/ouza/kifu/60/ouza201210030101.html
References
- Fairbairn, John (1986). Shogi for beginners (2nd ed.). Ishi Press. ISBN 978-4-8718-720-10.
- Hosking, Tony (1997). The art of shogi. Stratford-upon-Avon, England: The Shogi Foundation. ISBN 978-0953108909.