X-Git-Url: http://winboard.nl/cgi-bin?a=blobdiff_plain;f=doc%2Fgnushogi.info-1;fp=doc%2Fgnushogi.info-1;h=0000000000000000000000000000000000000000;hb=48e91ef03a032a541100743df1fd083696a5d3cd;hp=e37ba55241c52fea5fb6c3a1b5aac4a523879880;hpb=8ce8026a83784396ecdb1cc1530ab09c7ae0a53c;p=gnushogi.git diff --git a/doc/gnushogi.info-1 b/doc/gnushogi.info-1 deleted file mode 100644 index e37ba55..0000000 --- a/doc/gnushogi.info-1 +++ /dev/null @@ -1,1080 +0,0 @@ -This is gnushogi.info, produced by makeinfo version 4.3 from -gnushogi.texinfo. - - This file describes how to use GNU shogi, a program which plays -Shogi (Japanese chess). - - Copyright (C) 1999 Michael C. Vanier and the Free Software -Foundation, Inc. - - Permission is granted to make and distribute verbatim copies of this -manual provided the copyright notice and this permission notice are -preserved on all copies. - - Permission is granted to copy and distribute modified versions of -this manual under the conditions for verbatim copying, provided that -the entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - - Permission is granted to copy and distribute translations of this -manual into another language, under the above conditions for modified -versions, except that this permission notice may be stated in a -translation approved by the Free Software Foundation. - - -File: gnushogi.info, Node: Top, Next: (dir), Prev: (dir), Up: (dir) - -GNU Shogi (Japanese chess) -************************** - -* Menu: - -* Introduction:: What is GNU shogi? -* License:: The GNU General Public License. -* About shogi:: General information, rules, etc. -* gnushogi:: How to play GNU shogi (gnushogi). -* xshogi:: The X interface to GNU shogi. -* References and links:: Where to go for more information. -* Acknowledgements:: -* Bugs:: Where and how to report bugs. -* Index:: - - -File: gnushogi.info, Node: Introduction, Next: License, Prev: Top, Up: Top - -Introduction -************ - - GNU shogi is a program that plays shogi, the Japanese version of -chess, against a human (or computer) opponent. This file describes how -to use GNU shogi and also gives background information about the game -of shogi. - - This file describes GNU shogi version 1.3.2. It was written by me, -Mike Vanier, the current maintainer of GNU shogi. My email address is -. - - GNU shogi is actually two programs: - - -`gnushogi' - is the text-based program which also contains the game-playing - engine. - -`xshogi' - is the X-windows graphical interface to gnushogi. - - - Since xshogi invokes gnushogi, most players will just type "xshogi" -and start playing. - - Disclaimer: I use the personal pronouns "him", "his" etc. to refer -to a shogi player regardless of gender. That's easier than writing -"his or her" all over the place. I don't mean to infer that women -don't play shogi; in fact shogi is very popular in Japan among women as -well as men. - - -File: gnushogi.info, Node: License, Next: About shogi, Prev: Introduction, Up: Top - -GNU GENERAL PUBLIC LICENSE -************************** - - Version 2, June 1991 - Copyright (C) 1989, 1991 Free Software Foundation, Inc. - 675 Mass Ave, Cambridge, MA 02139, USA - - Everyone is permitted to copy and distribute verbatim copies - of this license document, but changing it is not allowed. - -Preamble -======== - - The licenses for most software are designed to take away your -freedom to share and change it. By contrast, the GNU General Public -License is intended to guarantee your freedom to share and change free -software--to make sure the software is free for all its users. This -General Public License applies to most of the Free Software -Foundation's software and to any other program whose authors commit to -using it. 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It is safest -to attach them to the start of each source file to most effectively -convey the exclusion of warranty; and each file should have at least -the "copyright" line and a pointer to where the full notice is found. - - ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES. - Copyright (C) 19YY NAME OF AUTHOR - - This program is free software; you can redistribute it and/or modify - it under the terms of the GNU General Public License as published by - the Free Software Foundation; either version 2 of the License, or - (at your option) any later version. - - This program is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU General Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software - Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. - - Also add information on how to contact you by electronic and paper -mail. - - If the program is interactive, make it output a short notice like -this when it starts in an interactive mode: - - Gnomovision version 69, Copyright (C) 19YY NAME OF AUTHOR - Gnomovision comes with ABSOLUTELY NO WARRANTY; for details - type `show w'. - This is free software, and you are welcome to redistribute it - under certain conditions; type `show c' for details. - - The hypothetical commands `show w' and `show c' should show the -appropriate parts of the General Public License. Of course, the -commands you use may be called something other than `show w' and `show -c'; they could even be mouse-clicks or menu items--whatever suits your -program. - - You should also get your employer (if you work as a programmer) or -your school, if any, to sign a "copyright disclaimer" for the program, -if necessary. Here is a sample; alter the names: - - Yoyodyne, Inc., hereby disclaims all copyright interest in the program - `Gnomovision' (which makes passes at compilers) written by James Hacker. - - SIGNATURE OF TY COON, 1 April 1989 - Ty Coon, President of Vice - - This General Public License does not permit incorporating your -program into proprietary programs. If your program is a subroutine -library, you may consider it more useful to permit linking proprietary -applications with the library. If this is what you want to do, use the -GNU Library General Public License instead of this License. - - -File: gnushogi.info, Node: About shogi, Next: gnushogi, Prev: License, Up: Top - -About the game of shogi -*********************** - - "Japanese chess cedes nothing in depth or beauty to the European - game... it is at least as interesting." - - -- Alexander Alekhine - (quoted in David Pritchard, `The Encyclopedia of Chess Variants') - - - "... shogi [is] by far the most complex form of chess that has ever - achieved widespread popularity." - - -- R. Wayne Schmittberger, `New Rules for Classic Games' - - - Shogi is the version of chess played in Japan. It is strikingly -different from standard chess (which I shall refer to henceforth as -"international chess") and also to all other regional variants, because -captured pieces can re-enter play on the side of the capturer. This -has several interesting effects on the play of the game: - - - 1. Shogi is much more complex than international chess, at least in - terms of the average number of possible moves per turn (estimated - at about 35 for chess and at about 80 for shogi). - - 2. There are almost no draws (about 1-2% of all games in professional - play). - - 3. Exchanges complicate the play rather than simplifying it. - - 4. There are no "endgames" in the standard chess sense; all pieces - remain in play throughout the game. Games typically end in a race - to checkmate the other player before being checkmated oneself. - - 5. Ownership of a piece is not indicated by the color of the piece; - instead, pieces are wedge-shaped and point towards the opponent. - The name of the piece is inscribed in Kanji characters on the - front of the piece. - - 6. Most importantly: it's more fun than other forms of chess :-) - - - - Shogi is extremely popular in Japan; it has been estimated that 20 -million Japanese can play shogi, of which perhaps 1 million are active -players. It is even more popular there than the game of go, Japan's -other favorite board game. There are a number of professional players -who make a considerable amount of money playing in shogi tournaments, -and the game receives extensive newpaper and television coverage. -Despite this, the game has yet to become popular outside of Japan. Part -of this is because the Kanji characters on the pieces scare away some -people, but mostly it's due, I think, to lack of exposure to the game -and to the difficulty of finding opponents. I hope that GNU shogi will -help introduce shogi to a wider audience. - -* Menu: - -* The rules of shogi:: -* Sample game:: -* Mating problems:: -* Shogi variants:: -* Differences between shogi and chess:: - - -File: gnushogi.info, Node: The rules of shogi, Next: Sample game, Prev: About shogi, Up: About shogi - -The rules of shogi -================== - - Shogi is a two-person abstract strategy board game with full -information (i.e. all pieces and moves are visible to both players at -all times). It is in the chess family, being descended from the same -ancestral game as international chess: the Indian game of Chaturanga. -The two players are referred to as "Black" and "White", with Black -moving first (unlike in international chess, where White moves first), -and with movement alternating between the two players. Note that -"Black" and "White" are just names; the pieces are not colored. -Instead, they are flat, wedge-shaped pieces which point towards the -opponent. The identity of a given piece is indicated by two Japanese -Kanji characters on each piece. In fact, only the top character is -needed to identify the piece and thus only the top character is used in -shogi diagrams. I will use alphabetical equivalents in the diagrams -here; to see what the Kanji characters look like, start up xshogi -(*note xshogi::) and compare the starting setup there with the starting -setup in this file (*note The opening setup::). - - The object of the game is to capture the opponent's King. The board -is a grid of 9x9 uncolored squares, and pieces are placed on the -squares. Each player begins with 20 pieces, described in the next -section. Capture is by displacement, as in international chess. - -* Menu: - -* The moves of the pieces:: -* The opening setup:: -* Promotion of pieces:: -* Drops:: -* Winning the game:: -* Draws:: -* Handicaps:: -* Notes for chess players:: - - -File: gnushogi.info, Node: The moves of the pieces, Next: The opening setup, Prev: The rules of shogi, Up: The rules of shogi - -The moves of the pieces ------------------------ - - Each player at the beginning of a shogi game has a total of 20 -pieces of eight different types. The moves of the shogi pieces can be -divided into three classes: "stepping" pieces, that only move one -square at a time; "ranging" pieces that move any number of unobstructed -squares in a line, and "jumping" pieces that can jump over obstructing -pieces to reach their destination squares. Most pieces can also -promote to different (usually stronger) pieces under certain -circumstances (see the next section). All pieces capture the same way -that they move (even pawns). The piece moves and promotions are as -follows; each piece name is followed by the standard piece abbreviation: - - 1. The king (K). The king can move one square in any horizontal, - vertical, or diagonal direction, just like the king in - international chess. The king does not promote. - - 2. The rook (R). The rook can move any number of squares in a - horizontal or vertical direction. The rook is the same as the - rook in international chess (except that it can promote). A rook - promotes to a "dragon king" or "dragon" for short (often just - referred to as a "promoted rook"), which can move as a rook or can - move one square in any diagonal direction. - - 3. The bishop (B). The bishop can move any number of squares in a - diagonal direction. The bishop is the same as the bishop in - international chess (except that it can promote). A bishop - promotes to a "dragon horse" or "horse" for short (often just - referred to as a "promoted bishop"), which can move as a bishop or - can move one square in any horizontal or vertical direction. - Note: the horse should not be confused with a knight (see below), - as they are two completely different pieces. - - 4. The gold general (G). A gold general can move one square in any - horizontal or vertical direction, or one square in a forward - diagonal direction. Gold generals do not promote. - - 5. The silver general (S). A silver general can move one square in - any diagonal direction, or one square straight forward. A silver - general promotes to a gold general. - - 6. The knight (N). A knight can move one square straight forward - followed by one square to either forward diagonal, jumping over - intervening pieces if any. In other words, a knight moves like - its international chess counterpart, but forward only. A knight - promotes to a gold general. The knight is the only jumping piece, - as in chess. - - 7. The lance (L). A lance can move any number of squares straight - forward. A lance promotes to a gold general. - - 8. The pawn (P). A pawn can move one square straight forward. The - pawn captures the same way that it moves, in contrast to - international chess. There is also no initial two-space move for - pawns and no _en-passant_ capture. A pawn promotes to a gold - general; a promoted pawn is usually known as a "Tokin". - - - -File: gnushogi.info, Node: The opening setup, Next: Promotion of pieces, Prev: The moves of the pieces, Up: The rules of shogi - -The opening setup ------------------ - - The opening setup for shogi is as follows: - - 9 8 7 6 5 4 3 2 1 -+--------------------------------------------+ -| wL | wN | wS | wG | wK | wG | wS | wN | wL | a -+--------------------------------------------+ -| | wR | | | | | | wB | | b -+--------------------------------------------+ -| wP | wP | wP | wP | wP | wP | wP | wP | wP | c -+--------------------------------------------+ -| | | | | | | | | | d -+--------------------------------------------+ -| | | | | | | | | | e -+--------------------------------------------+ -| | | | | | | | | | f -+--------------------------------------------+ -| bP | bP | bP | bP | bP | bP | bP | bP | bP | g -+--------------------------------------------+ -| | bB | | | | | | bR | | h -+--------------------------------------------+ -| bL | bN | bS | bG | bK | bG | bS | bN | bL | i -+--------------------------------------------+ - - - Here, "b" stands for "black" and "w" stands for "white", so that, -for instance, "bL" means "black lance". The numbers above the files -and the letters to the right of the ranks represent the most common -notation system used for shogi by westerners (the Japanese also use -Arabic numerals for the files but use Japanese numerals for the ranks). - - -File: gnushogi.info, Node: Promotion of pieces, Next: Drops, Prev: The opening setup, Up: The rules of shogi - -Promotion of pieces -------------------- - - In sharp contrast to international chess, where only pawns can -promote to higher-ranked pieces, most of the pieces in shogi can -promote. The promoted ranks are discussed in the section on piece -moves (*note The moves of the pieces::) but are repeated here for -reference: - -Pawn - promotes to gold general (called a `tokin' in this case only). - -Lance - promotes to gold general. - -Knight - promotes to gold general. - -Silver general - promotes to gold general. - -Gold general - does not promote. - -Bishop - promotes to "dragon horse" or just "horse" for short. The horse - can move as a bishop or can move one square in any orthogonal - direction. - -Rook - promotes to "dragon king" or just "dragon" for short. The dragon - can move as a rook or can move one square in any diagonal - direction. - -King - does not promote. - - - The three ranks furthest away from each player constitute his/her -"promotion zone". A player may, but is not required to, promote a -piece after making a move in which the piece begins and/or ends in the -promotion zone. Thus you can promote a piece when moving the piece into -the promotion zone, out of the promotion zone, or entirely within the -promotion zone. Promotion is mandatory in these cases: - - - 1. You must promote a pawn or a lance after moving it to the last - rank. - - 2. You must promote a knight after moving it to either of the last - two ranks. - - - - These forced promotions ensure that a piece cannot be moved to a -square from which it would have no further move. - - Pieces "dropped" onto the board (*note Drops::) always drop in the -unpromoted state, even if they drop into the promotion zone. - - -File: gnushogi.info, Node: Drops, Next: Winning the game, Prev: Promotion of pieces, Up: The rules of shogi - -Drops ------ - - When a player captures a piece, that piece is not removed from play. -Instead, it becomes the property of the capturer and can re-enter play -by being placed on (almost) any vacant square during the player's move. -This is known as a "drop" and counts as a full move (in other words, -you can either move a piece on the board or drop a piece onto the board -during your move, but not both). All pieces drop in the unpromoted -state. Pieces may be legally dropped in their promotion zone, but they -do not promote on that turn. - - There are several restrictions on drops: - - 1. A pawn may not be dropped onto a file if there is already an - unpromoted pawn belonging to the same player on that file. It is - legal to drop a pawn on a file which contains a _promoted_ pawn - belonging to the same player, however. - - 2. A pawn may not be dropped to give immediate checkmate on the move. - A pawn is, however, permitted to be moved on the board to give - immediate checkmate. This is a curious rule, and if anyone knows - the reason for it I would appreciate it if they would contact me - and explain it to me :-) - - 3. A pawn or piece may not be dropped onto a square from which they - would have no legal move. This means that pawns and lances may - not be dropped onto the last rank, and the knight may not be - dropped onto the last or second-to-last rank. - - - It is entirely permissible (and often advisable) to drop a piece or -pawn between one's King and an attacking ranging piece. For this -reason, the final checkmating move is nearly always an attack on the -King from an adjacent square (except for an attack by a Knight). - - Captured pieces are said to be pieces "in hand". - - The drop is the primary distinguishing feature of Japanese chess, -shared with no other popular chess-type game. It gives shogi a very -aggressive quality, and dramatically increases the number of possible -moves once a few pieces have been captured. Another interesting -feature of shogi is that exchanges complicate play rather than -simplifying it (as in international chess), because of the drop rule. - - -File: gnushogi.info, Node: Winning the game, Next: Draws, Prev: Drops, Up: The rules of shogi - -Winning the game ----------------- - - A game of shogi is won by capturing the opponent's king. In general, -this is done by checkmating the king: attacking the king in such a way -that the king cannot be defended no matter what the defending player -moves. Note, though, that there is no rule that requires a player to -defend a king which is being attacked. However, if he does not defend -his king, the opponent is entirely free to capture it on the next move, -thus winning the game. As in international chess, in practice most -games end by resignation when one player realizes that he cannot escape -checkmate. - - -File: gnushogi.info, Node: Draws, Next: Handicaps, Prev: Winning the game, Up: The rules of shogi - -Draws ------ - - There are very few draws in shogi; only about 1-2% of professional -games end in a draw. One reason for this is that material can never be -depleted as in chess, because captured pieces are constantly re-entering -play as a consequence of the drop rule. In fact, most of the ways a -game can be drawn in chess are not allowed in shogi: - - - * Draws cannot be offered. - - * There is no fifty-move rule. - - * A stalemate counts as a win for the stalemater. Stated otherwise: - if you can't move, you lose. - - * Perpetual check is illegal (see below). - - - - There are only two legal ways in which a draw can occur: - - - 1. A position (including the pieces in hand) occurs 4 times with the - same player to move (called "Sennichite"). However, if this is - caused by consecutive checks (direct attacks on the King, - threatening to capture it on the next move) by one side, the - player giving these checks loses the game. In other words, - perpetual check results in a loss for the attacker who recreates - the same position the 4th time. - - 2. Both players have moved their King into the the promotion zone (or - they cannot be prevented from doing so) and the Kings cannot be - checkmated. A King who has entered the promotion zone is known as - an "entering King"; due to the forward orientation of most shogi - pieces, it is very hard to mate such a King. In that case the - players may decide to count their pieces as follows: the King does - not count, the Rook and Bishop count as 5 points, and all other - pieces as one point. Promotion is disregarded. If both players - have at least 24 points the game is a draw (called "Jishogi"). If - a player has less, he loses the game. - - Of course, a player can refuse to count pieces when he still has - mating chances or chances to gain material which would affect the - outcome of the counting. There is no strict rule about what to do - if this is not the case, but nonetheless a player refuses to count - up (e.g. because he does not have enough points for a draw). It - has been generally accepted that in such a case the game ends and - the pieces are counted after one player has managed to get all his - pieces protected in the promotion zone. - - - - -File: gnushogi.info, Node: Handicaps, Next: Notes for chess players, Prev: Draws, Up: The rules of shogi - -Handicaps ---------- - - Unlike international chess, shogi has a well-established handicap -system which is used when players of different strengths play against -each other. Handicaps range from small to huge, which makes it -possible for weak players to play against even very strong players and -have an even chance of winning. - - Shogi players are ranked as follows: the weakest rank is around 15 -"kyu", which represents a beginner. 14 kyu is higher than 15 kyu, 13 -kyu is higher still, and so on until you get to 1 kyu. The next highest -rank is 1 "dan", followed by 2 dan, 3 dan and so forth. The highest -amateur rank is 6 dan; professionals go up to 9 dan. However, -professional ranks are not the same as amateur ranks; a professional 1 -dan is _much_ stronger than an amateur 1 dan. This system is similar -to that used by go players (and also other Japanese sports such as -karate). - - A handicap consists of the stronger player playing White and removing -one or more pieces from his side of the board at the start of the game. -These pieces are permanently removed from play; they are not in hand. - - The following is a list of the accepted handicaps, from weakest to -strongest. The degree of the handicap, represented by the position in -the list, represents the difference in rank between the two players for -which the handicap is appropriate. These rules are taken from the books -"Shogi for Beginners" by John Fairbairn and "The Art of Shogi" by Tony -Hoskings (*note References and links::) and, I believe, represent -current Japanese practice. - - - 1. The stronger player removes his left lance (on 1a). - - 2. The players play a two-game match; in the first game the stronger - player removes his left lance (on 1a), while in the second game he - removes his bishop. - - 3. The stronger player removes his bishop. - - 4. The stronger player removes his rook. - - 5. The stronger player removes his rook and left lance. - - 6. The players play a two-game match; in the first game the stronger - player removes his rook and left lance (on 1a), while in the - second game he removes his rook and bishop. - - 7. The stronger player removes his rook and bishop. This is usually - called a "two-piece" handicap. - - 8. The stronger player removes his rook, bishop, and both lances. - This is called a "four-piece" handicap. - - 9. The stronger player removes his rook, bishop, both lances, and both - knights. This is called a "six-piece" handicap. - - 10. The stronger player removes his rook, bishop, both lances, both - knights, and both silvers. This is called an "eight-piece" - handicap. - - - - Another advantage of playing handicap games is that the handicaps -alter the optimal strategy for both players. For instance, handicaps -all have their own opening lines which may bear little or no -resemblance to those used in non-handicap shogi. This means that when -learning handicap shogi, you are essentially learning completely new -games which use the same equipment! - - The reader may wonder how on earth a player giving an eight-piece -handicap, say, could possibly hope to win. Don't forget, though, that -in shogi the opponent's pieces can be captured and then become part of -one's own army. Thus, if the opponent plays badly enough, the number of -pieces will soon even out. - - -File: gnushogi.info, Node: Notes for chess players, Prev: Handicaps, Up: The rules of shogi - -Notes for chess players ------------------------ - - Here are a few miscellaneous things that may confuse chess players. -Some of these have been mentioned elsewhere, but they bear repeating. - - - 1. There is no queen. - - 2. Pawns capture the same way they move. There is no initial - two-space pawn move and no _en-passant_ move. - - 3. There is no special castling move. There _are_ a large number of - possible defensive formations referred to as "castles" (*note - Sample game::) but there is no need for special moves to create - them. - - 4. A given piece can only promote to _one_ other kind of piece. - - - - -File: gnushogi.info, Node: Sample game, Next: Mating problems, Prev: The rules of shogi, Up: About shogi - -Sample game -=========== - - This game was annotated by Pieter Stouten (*note References and -links::). I have made some minor corrections. Note that captures are -denoted by the "x" symbol e.g. Rx3f and drops are denoted by the "*" -symbol e.g. R*3f. Check is indicated by a "+" after the move, e.g. -R3f+. I recommend you use gnushogi/xshogi to play along with this -game. In xshogi simply hit the "Force Moves" button after starting up, -while in gnushogi enter the word "force" at the prompt. This will -allow you to enter moves for both sides. - - Note also that the move numbering system used here is the chess-type -system where one move means one move by each player. The Japanese count -one move made by each player as two moves. - --------------------------------------------------------------------------- - - Below you will find (the English translation of) an annotated game -which was published in the Dutch Shogi magazine "81" and in the Dutch -beginners booklet. It has proven to be a very useful game to explain -some basic principles of Shogi. Also, it is a rather straightforward -game compared to professional games where in most cases very diffuse -middle game fights take place. - - Pieter Stouten, 14th May 1990. - --------------------------------------------------------------------------- - - Black: Michael Trent (1-dan). White: David Murphy (2-dan). - - 1. P2f P3d 2. P2e B3c -[ This move is necessary, as otherwise white can exchange pawns: 3. P2d -Px2d 4. Rx2d. He would thus get a pawn in hand and open up his rook -file. ] - - 3. P7f P4d -[ White closes the bishop diagonal again. He plans to play ranging rook -(the rook goes to 5b, 4b, 3 or 2b; a defensive strategy) and in that -case he'd better avoid an exchange of bishops. One of the reasons is -that he will have problems developing his pieces without leaving holes -for bishop drops. ] - - 4. S4h R3b 5. P3f S4b 6. K6h K6b -[ In general the rook plays an important role in the attacks. It is -wise to move the king away from the area where the initial fights will -be and both players act according to the Shogi proverb "keep the rook -and king apart". ] - - 7. K7h K7b 8. P5f P5d 9. G4i-5h G4a-5b -[ Both players use their second gold general to build their castle. ] - - 10. S6h -[ In itself this move is not bad. However, it will become clear that -black plans a quick attack and in that case it is wiser to omit this -move. ] - - 10... S5c 11. P1f P1d -[ The advance of the edge pawns must be timed very well. The remark at -black's tenth move applies here too: this move is good if black wants to -play a slow game, because it eliminates a future B1e. ] - - 12. P4f K8b 13. N3g S7b -[ Black develops his knight in order to start an attack over the second, -third and fourth files. White strengthens his king's position and -awaits the attack. He aims at a counterattack as soon as black has -broken through into the white camp. Probably white's breakthrough will -take place later, but he has good compensation in the form of a stronger -castle. This theme occurs very often in static rook versus ranging rook -games. ] - - 14. P4e R4b -[ Black starts his attack and white puts up a very passive defence. His -rook has a hard task now to penetrate the black position. Moreover, he -blocks his own bishop. It seems much better to start a counterattack -with 14... P3e, later to be followed by B2b, B5a or Bx4d in order to use -his rook more actively. ] - - 15. Px4d Sx4d 16. P*4e S5c -[ 16... Sx4e is more active. A silver general is normally more valuable -than a knight, but white gets two pawns in hand and black none, while -the knight might come in handy for white too. ] - - 17. Bx3c+ Nx3c 18. P2d Px2d -[ Black threatens to break through and white has to consider taking the -pawn on 2d or starting a counterattack with Nx4e. If he chooses the -latter, black can play Px2c+ followed by +P3c. The disadvantage is the -black "tokin" (=promoted pawn) that white will get in his camp; the -advantage is that it will cost black two more moves to promote his rook. -Because white did not trust that the result after engaging in a -"semeai" (=mutual attack) with 18...Nx4e would give a positive result, -he captured the pawn on 2d. Making the right decision in moments like -this often makes the difference between a win and a loss: miss one -attacking chance and you will be forced to defend the whole game until -the unavoidable defeat; on the other hand, an unsound attack can destroy -all "aji" (=potential, meaning possibilities, threats) without getting -anything in return. ] - - 19. Rx2d Nx4e 20. Nx4e Rx4e 21. R2a+ P*4g -[ Now it becomes clear why black's 10. S6h was not good. Had this move -been omitted, then white would not have had the time to play 13... S7b -and after R2a+ the gold on 6a would hang. Thus black would have kept -"sente" (=initiative). Instead of 21... P*4g, B*6d is a very good -move, because after 22. P*2h black does not have a pawn in hand anymore -and he is being threatened with the annoying 22... N*4f 23. G5g N3h+ -24. S4g +N4h also. Black can also counter 21... B*6d with 22. N*3g. -White would then reply with 22... R4b 23. B*3c P*4g 24. Bx4b+ Sx4b. The -white rook has played its role and instead of spending moves on saving -it white starts to scatter black's defences by successive pawn drops on -the fourth file: 25. Gx4g P*4f 26. G5g N*6e 27. G5h P4g+ 28. Gx4g P*4f. -This analysis was provided by Kato Hifumi, 9-dan professional (the -highest regular grade). Destroying the coherence of the enemy pieces -(their shape) by dropping pawns is one of the most important Shogi -techniques. With the actual move 21... P*4g white missed a good -chance. ] - - 22. Sx4g P*4f 23. B*3g Px4g+ 24. +Rx6a +Px3g -[ 23. B*3g seems pointless, but a closer look reveals that it is -actually quite mean. On move 24 white cannot capture black's "Ryu" -(=dragon =promoted rook) with his silver: 24... Sx6a 25. N*7d K7b 26. -G*8b mate. By attacking the front of the white castle and threatening -to mate him there, black has the chance to break down the white -defences from the side. ] - - 25. +Rx5b S*6b -[ Here 25... B*4d would be much better, because it is defensive and -attacking at the same time. After e.g. 26. G*4c Bx9i+ 27. Gx5c black -threatens 28. +Rx7b Kx7b 29. S*6a K8b 30. S*7a Kx7a 31. G*7b mate. -White is one move quicker, however. He has the following beautiful -"tsume" (mating sequence where every move is check): 27... N*8f 28. Px8f -S*8g 29. Kx8g B*9h 30. K7h Bx8i+ 31. K8g +B8i-8h 32. K9f L*9e mate. -This illustrates the sharpness of Shogi: one move can make the -difference between winning and losing. ] - - 26. P*4f Rx4f -[ This move eliminates white's last chances. 26... R4b 27. +Rx4b Sx4b -28. R*4a seems annoying, but after 28... B*3c 29. S7g B*3b white wins -the rook and with his "tokin" on 3g there still is some hope. ] - - 27. N*6e +P4g -[ White cannot defend anymore, so he starts a desperate attack. Black -does not lose the right track, however. ] - - 28. Nx5c+ +Px5h 29. +Nx6b +Px6h 30. Gx6h N*8f 31. Px8f B*6i 32. -Gx6i R4h+ 33. N*6h +Rx6h 34. Gx6h S*8g 35. Kx8g N*9e 36. K7h -Resigns -[ White resigns here, because after 36... B*8g 27. K7g his attack has -petered out. ] -