Shogi strategy and tactics

From Wikipedia, the free encyclopedia
Jump to: navigation, search

Shogi, like western chess, can be divided into the opening, middle game and endgame, each requiring a different strategy. The opening consists of arranging one's defenses and positioning for attack, the middle game consists of attempting to break through the opposing defenses while maintaining one's own, and the endgame starts when one side's defenses have been compromised.

Tactics[edit]

The basic tactics (手筋 tesuji) of shogi are similar to those of chess tactics, involving forks, pins, removing the defender and other techniques, all of which are considered very strong when used effectively. Other tactics, particularly ones involving dropped pieces, have no parallel in western chess.

Fork[edit]

A fork (両取り ryōtori) is a move that uses one piece to attack two or more of the opponent's pieces simultaneously, with the aim to achieve material advantage, since the opponent can counter only one of the threats.[1]

Some forks have specific names in Japanese. A silver forking two pieces from behind is 割り打ちの銀 wariuchi no gin "silver stabbing-in-the-back". A fork between a king and a rook is 王手飛車 (ōtebisha).

Pin[edit]

Bishop Pinning Pawn
Protecting Rook
△ pieces in hand:
9 8 7 6 5 4 3 2 1  
                  a
                  b
                  c
                  d
                e
                  f
                g
                h
                  i
▲ pieces in hand:

A pin (合駒 or 合い駒 aigoma) is when a defending piece that is attacked by a ranging piece cannot move without exposing a more valuable piece behind it.[1] (Cf. also skewers.) In shogi, only lances, rooks (or dragons), and bishops (or horses) can pin an opponent's piece.

In the adjacent example, the Black's pawn at 3g is pinned by White's bishop because if the pawn were to advance to 3f then Black's rook would be captured by the bishop.

Rook Pinned to King by Bishop
△ pieces in hand:
9 8 7 6 5 4 3 2 1  
      a
                  b
          c
              d
                e
                  f
                  g
                  h
                  i
▲ pieces in hand:

The most powerful pins are ones involving a king, which causes the pinned piece to be absolutely immobile.

Piece sacrifice[edit]

(Cf. sacrifices in western chess.)

Striking pawn[edit]

A striking pawn (叩きの歩/たたきの歩 tataki no fu) is the tactic of dropping a pawn directly in front of an opponent's piece immediately attacking it. The desired effect of this tactic is usually to force the opponent to move their pieces in a certain way in reaction to the threat of the striking pawn.

Dangling pawn[edit]

A dangling pawn or hanging pawn, (垂れ歩/たれ歩 tarefu or 垂らし歩 tarashifu) is a pawn that is dropped in a position in which it can promote (to a と tokin) in the player's next move.[2] (The act of dangling the pawn is 垂らし tarashi.)

Although dropping a dangling pawn may not be an immediate threat to an opponent, the later threat of promotion can be a greater danger.

For example, in the diagrams below, Black is attempting to break through White's camp along the second file at 2c with a dropped pawn supported by a rook on 2h. If Black drops the pawn on 2c, White can retreat their bishop to 3a and since the pawn can only attack forward it does not threaten Black's gold on 3c. In subsequent moves, Black cannot win the piece exchanges by promoting the pawn on the b rank (P-2b+) because White can start the attack and there are an equal number of pieces (gold and bishop vs pawn and rook).

In contrast, if Black drops a dangling pawn to 2d and White does nothing to prepare, when the pawn promotes at 2c both White's gold and bishop will be attacked by the tokin.

Joining pawns[edit]

Joining pawns (継ぎ歩 tsugifu) is a tactic in which a pawn is sacrificially dropped at the head of an opponent's pawn in order to lure the opponent's pawn forward.

In the example diagrams, Black attacks White's pawn on 2c leading White to capture Black's pawn. Then, Black plays the joining pawn tactic forcing White to move to 2e. Since White's pawn is now at 2e it cannot be used to protect White's camp on the second file. Furthermore, since White cannot drop a second pawn on the second file, their defense is much weaker.

Additionally, the moved pawn also gives Black an option of dropping a dangling pawn on 2d, which cannot be immediately attacked by White. This joining–dangling pawn sequence corresponds to a shogi proverb: 三歩あったら、継ぎ歩とたれ歩 sanpu attara tsugifu ni tarefu "if you have three pawns, joining pawn and dangling pawn".[3]

Joining pawn tactics may be useful in damaging the structure of an opponent's castle.

Piece exchange and turn loss[edit]

When two pieces (usually identical) are captured by each side at the same coordinates, it is referred to as an exchange. (Cf. exchanges in western chess.) Since captured pieces are never removed from play, a piece exchange has the effect of putting the exchanged pieces in hand and a turn sacrifice for the player who initiated the exchange. (See also: Tempo.)

For example, in the diagrams to the right, Black has decided to capture White's bishop on 2b with their bishop on the seventh file (Bx2b). White responds by capturing Black's bishop with White's silver (Sx2b). In comparing the start and end board positions of this bishop exchange, one can see that this is as if Black and White both removed each of their bishops from the board and put them each in hand and then Black skipped their turn allowing White to advance their silver to 2b. For this reason, equal piece exchanges must weigh the pros and cons of losing a turn and gaining a piece in hand (all else being equal).

There is an opening known as Tempo Loss Bishop Exchange, which is so-named because White, who already is slower to position their pieces since they have second move, intentionally skips their turn via a bishop exchange. This puts White behind two moves. (Of course, there is a strategical tradeoff in this move which allows White to position their pieces in way that isn't otherwise possible.)

Generals[edit]

Function and mobility[edit]

Golds are usually used to defend whereas silvers are used to attack.

Dancing Pawns[edit]

Dancing Pawns (ダンスの歩 dansu no fu) is a pawn drop and pawn sacrifice tactic that exploits the limited piece movement of the gold.[4]

The name comes from the way that the pawns cause the gold (or golds) to move around as if they were dancing in their futile attempt to escape capture.

Mating with gold[edit]

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 ("stomach-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 an gold in hand during the endgame so that a mate with a dropped gold can be executed.[5]

Mating and promotion[edit]

Since mate by gold is a fundamental checkmate tactic in shogi, it is common for pieces to promote into a gold to deliver checkmate.[6]

For instance, a silver defended by a pawn can mate at the head of a king but only if the silver promotes to a gold as with S-5b+.[a] An unpromoted silver here (S-5b=) cannot attack the side squares (6b, 4b) leaving two escape routes for the king.

As another example, a knight may mate a king if promoted to a gold as well (as shown in the diagrams to the right). If the knight didn't promote here, then there would be no checkmate.

In other situations, staying unpromoted can lead to a mate while promoting does not result in mate.[6] In the example, if the knight on 8e moves to 7c and does not promote, it attacks the king and delivers checkmate (since the horse is also attacking the b rank squares in front of the king). However, if the knight moved to 7c and promoted to the gold-like narikeima, then the promoted knight isn't attacking the king leaving White a chance to counterattack to avoid checkmate.

The same is true with the silver example to the right. If the silver promoted at 8c, then it would not be checkmate since a gold-like promoted silver cannot attack backwards diagonally.

Edge attack[edit]

An edge attack (端攻め hashizeme) is an attack on the first or ninth files of an opponent's camp. This is a common tactic since there is a limit on the number of pieces that can protect the edge files.

One edge attack tactic is dropping a pawn behind an opponent's lance and threatening to promote it once the lance has been lured forward.[7]

For instance, in the diagrams to the right, Black can move their first file pawn to 1d attacking White's pawn. Black's pawn will be sacrificed after White captures it leaving an open space on 1c for White's lance to move to in subsequent moves. After the pawn capture, Black can utilize their three pawns in hand by dropping a sequence of sacrificial pawns on the first file directly attacking White's lance. After White's lance is positioned on 1c, Black can now drop a pawn behind lance and then promote it to a tokin on 1a later for use within White's camp.

Relative piece value[edit]

Shogi pieces may be considered to have different valuations in which some pieces are generally more valuable than others – all other things being equal. (Cf. piece value in western chess.)

There are three main valuation groups:[8]

  1. the king which has an absolute value since the game is lost if mated
  2. the two major (most mobile) ranging pieces (大駒 oogoma): rook, bishop
  3. the minor pieces (小駒 kogoma): pawn, lance, knight, silver, gold

The minor pieces can be further grouped in the following valuation hierarchy:

gold > silver > (knight, lance) > pawn

Sometimes, the relative pieces are formalized with specific numerical values. This is particularly common in the explicit formalizations found in computer shogi. For instance, Reijer Grimbergen uses the following relative values in a Move Merit Analysis formalization:[9]

Grimbergen
Piece Value
pawn 1
香, 桂 lance, knight 3
銀, 金 silver, gold 5
bishop 8
rook 9
promoted bishop 12
promoted rook 13

Grimbergen notes that, unlike western chess, shogi piece valuation is not standardized as different players disagree on the exact values.

Another formalization used by program YSS 7.0 of 1997 had the following relative values:[10]

YSS 7.0
Piece Value Piece in hand Value Promoted Piece Value
pawn 1.00 歩 手駒 pawn in hand 1.15 promoted pawn 4.20
lance 4.30 香 手駒 lance in hand 4.80 promoted lance 6.30
knight 4.50 桂 手駒 knight in hand 5.10 promoted knight 6.40
silver 6.40 銀 手駒 silver in hand 7.20 promoted silver 6.70
gold 6.90 金 手駒 gold in hand 7.80
bishop 8.90 角 手駒 bishop in hand 11.10 promoted bishop 11.50
rook 10.40 飛 手駒 rook in hand 12.70 promoted rook 13.00

Kouji Tanigawa (谷川浩司), Yasumitsu Satou (佐藤康光), and Larry Kaufman suggest the following values:[11][12][13]

Piece Tanigawa (1982) Tanigawa (NHK) Satou Kaufman Promoted Piece Tanigawa (1982) Tanigawa (NHK) Satou Kaufma
1 1 1 1 12 6 11 10
5 3 6 4 10 6 11 9
6 4 6 5 10 6 11 9
8 5 10 7 9 6 11 8
9 6 11 8
13 8 17 11 15 10 20 15
15 10 19 13 17 12 22 17

Under these valuation schemes, the promoted pawn, lance and knight all have a higher value than a gold even though when promoted they move the same as a gold. The reason for this is that they will return to their lesser values when captured by an opponent whereas a captured gold gives the opponent a relatively more valuable piece.

Nonetheless, Kaufman notes that exchanging a promoted pawn for a real gold is a good material gain tactic in contradiction to the relation implied by this scheme's relative values of promoted pawn and gold.

Relative piece valuations are used to roughly evaluate piece exchanges. For example, if there is an opportunity to capture two golds from an opponent by giving up a rook and a pawn, using Kaufman's scheme, this is seem as a favorable trade (all else equal):

(gold + gold) > (rook + pawn)
(8 + 8) > (13 + 1)

However, this wouldn't be a good trade if the rook was promoted:

(gold + gold) < (dragon + pawn)
(8 + 8) < (17 + 1)

Castles[edit]

Main article: Castle (shogi)
Ranging Rook Anaguma
△ pieces in hand:
9 8 7 6 5 4 3 2 1  
                  a
                  b
                  c
                  d
                  e
                  f
          g
            h
            i
▲ pieces in hand:

In shogi, strong defensive fortifications protecting the king are known as castles. There are many types of castles and variations which can be used, but it is essential to understand which ones are useful in the current situation and how to compensate for its weak points. Three commonly used castles are listed below.

The Yagura castle is considered by many to be the strongest defensive position in shogi.[14] A common Yagura structure is the Gold Yagura. It has a strongly protected king; a well-fortified line of pawns; and the bishop, rook, and a pawn all support a later attack by the rook's silver or knight. It is notoriously difficult to break down with a frontal assault, though it is weaker from the side. It is typically used against Static Rook openings that involve advancing the rook's pawn. However, one's opponent may just as easily adopt this defense, giving neither side an advantage.

A defensive position that is considered easier for beginners, but still popular with professionals, is the Mino castle. The King is placed in a safe position, while the three generals work well to back each other up. This is often used when a player chooses a Ranging Rook opening rather than the Static Rook opening.[15]

A third defense often used in professional shogi is the Anaguma castle, commonly called the "bear in the hole" castle in English. A player utilizing the Ranging Rook strategy uses a Ranging Rook Anaguma on the right side. The end result will place the king in the corner square where the lance started, defended by two gold generals and one silver. This way, the King cannot be easily checked by a knight or a ranging piece.[16]

Opening[edit]

Main article: Shogi opening

The opening of shogi is generally slower than that of chess, due to the larger board and less mobile pieces. But since a quick offense will leave a player's home territory open to drop attacks as soon as pieces are exchanged, the aim of the opening is to build up defenses for the king, typically by moving the king to the side in a castle with three generals.[17] Leaving a king on its original square (居玉 igyoku or "sitting king") is a particularly dangerous position.[14][18]

Both players can move the rook pawn forward (P-2f), or, more commonly, advance the pawn above and to the right of the bishop (P-7f). The former is known as a rook opening and the latter a bishop opening.

With a bishop opening, it's common to exchange bishops by having one capture the other. This allows each player to put their newly captured bishop into play anywhere on the board, although care must be taken to avoid weaknesses in defense which may allow for a bishop drop. However, it is not advantageous to exchange bishops if your opponent has a better defensive setup, or more lines of attack. Moreover, making a bishop exchange constitutes one turn loss, so it's not advised without a good reason.

Many common opening attacks involve advancing a silver and ideally pawns, protected by other pieces. Because silvers have more possibilities for retreat, while golds better defend their sides, silvers are generally considered superior as attacking pieces, and golds superior as defensive pieces. It is common practice to defend the king with three generals, two golds and a silver.

Because defense is so important, and because shogi pieces are relatively slow movers, the opening game tends to be much longer in shogi than in international chess,[14] commonly with a dozen or more moves to shore up defenses before the initial attack is made.

Over many decades, Japanese professional players have all invented various jōseki, which determine moves and sequences which are thought to be the best for a particular situation. It also covers a branch of different variations within an intricate strategy, including alternative options and the certain consequences that some moves may bring.[19]

Openings are also classified as Static Rook openings, where the offense is supported by the rook in its original position, and Ranging Rook openings, where the rook moves to the center or left of the board to support an attack there, typically with the idea of allowing the opponent to attack while arranging a better defense and aiming for a counterattack.[20] However, as the most powerful piece on the board, the rook invites attack, and in most cases, especially for weaker players, it is a good idea to keep the king well away from the rook.[14] Relatedly, the static vs ranging classification corresponds to castle development: static rook positions tend to have castles on the left side of the board while ranging rook positions tend to have castles on the right side.

Middle game[edit]

Professional shogi players tend to evaluate the flow of the game, that is, the sequence of moves leading to the current position and its likely development, much more than chess players.[21]

Because pawns attack head on, and cannot defend each other, they tend to be lost early in the game, providing ammunition for such attacks. Dropping a pawn behind enemy lines, promoting it to a tokin (gold general), and dropping a second pawn immediately behind the tokin so that they protect each other makes a strong attack; it threatens the opponent's entire defense, but provides little value to the opponent if the attack fails and the pieces are captured.

Players raised on international chess often make poor use of drops,[14] but dropping is half the game. If a player has more than a couple of captured pieces in hand, it is likely that dropping attacks are being overlooked. However, it is wise to keep a pawn in hand, and often to exchange pieces if necessary to get one.[22] Compared with international chess players, shogi players are more likely to sacrifice pieces, even powerful ones, if the resulting capture can be dropped back into play for a specific purpose.[23]

Attacking pieces can easily become trapped behind enemy lines, as the opponent can often drop a pawn on a protected square to cut off the line of retreat. For this reason, rooks, which can retreat in only one direction, are commonly kept at a safe distance in the early parts of the game, and used to support attacks by weaker pieces. However, once the game has opened up, a promoted rook is an especially deadly piece behind enemy lines.

Advancing a lance pawn can open up the side of the board for attack. Therefore, when a player first advances a lance pawn, it is common, though not obligatory, for the opponent to answer by advancing the opposing pawn, in order to avoid complications later in the game. It also allows the king to escape if attacked from the side.

End game[edit]

The collapse of one side's defense marks the beginning of the end game. Once a player has broken through the enemy lines, the opponent's king can be easily trapped by its own pieces. A common last-ditch defensive tactic is to open the pawn line to allow the king to escape. Kings are more difficult to checkmate in the open, especially if the opponent does not have many ranged pieces in play.

In the endgame, it comes down to a race over who can checkmate the opponent first. A tactic known as speed counting plays an important role in the endgame. By counting the number of moves until checkmate (assuming the opponent doesn't get to move) for both Black and White, this will help to influence decisions on whether to attack or defend. A simple mistake can change the flow of the game drastically. Among this, there are many other delicate factors to look out for within the endgame, including sacrificial attacks and traps.

A player's endgame play is strengthened by training on tsumeshogi.

See also[edit]

Notes[edit]

  1. ^ An unpromoted silver could only mate a king in a similar position if there was another piece behind it that attacked along the sides of the silver such as another silver, a gold, a horse, or a dragon.

References[edit]

  1. ^ a b Hosking 1997, p. 30–34, Part 1, Chapter 5: Introduction to shogi strategy and tactics: Forks and pins, The major pieces, The minor pieces.
  2. ^ Hosking 1997, p. 32–34, Part 1, Chapter 5: Introduction to shogi strategy and tactics:The Minor pieces.
  3. ^ 大平, 武洋 (2014). 必修!穴熊戦の絶対手筋105 (in Japanese). p. 39. ISBN 978-4-8399-5322-5. 
  4. ^ 加藤, 治郎 (1992). 将棋は歩から (in Japanese). pp. 188 ff. ISBN 978-4885-744105. 
  5. ^ Aono 2009, p. 192–196, Chapter 5: Improve your endgame: Lecture 1: The relationship with the type of piece: Calculating the number of pieces required for mate.
  6. ^ a b Leggett 1993, p. 25–42, Learning to use the pieces.
  7. ^ Kitao 2012, p. 5–32, Chap 1: Edge attack basics and middlegame technique: Edge attack basics.
  8. ^ Hosking 1997, p. 30, Part 1, Chapter 5: Introduction to shogi strategy and tactics: Relative major and minor pieces.
  9. ^ Grimbergen, Reijer (2001). "Plausible move generation using move merit analysis with cut-off thresholds in shogi". In Marsland, Tony; Frank, Ian. Computer and games. Springer. pp. 315–345. ISBN 3-540-43080-6. 
  10. ^ Yamamoto, Masahito; Suzuki, Keiji; Ohuchi, Azuma (2001). "An acquisition of evaluation function for shogi by learning self-play". International Transactions in Operational Research. 8: 305–315. 
  11. ^ Tanigawa 1982.
  12. ^ NHK将棋講座
  13. ^ Kaufman, Larry. "Handicap series: An introduction". Les parties à handicap par Larry Kaufman. 
  14. ^ a b c d e Fairbairn 1984.
  15. ^ Hosking 1997, pp. 49–50, Part 1, Chapter 8: Castles.
  16. ^ Hosking 1997, p. 53–54, Part 1, Chapter 8: Castles.
  17. ^ Grimbergen & Rollason 2003, p. 175, Board Maps for Opening and Middle Game Play in Shogi.
  18. ^ Hosking 1997, p. 42, Part 1, Chapter 7: Balancing Attack with Defense.
  19. ^ Hosking 1997, p. 29, Part 1, Chapter 5: Introduction to Shogi Strategy and Tactics.
  20. ^ Hosking 1997, pp. 43–45, Part 1, Chapter 7: Balancing Attack with Defense.
  21. ^ Ito, Takeshi; Matsubara, Hitoshi; Grimbergen, Reijer (2004). "Shōgi no Ninchi Kagakuteki Kenkyū (2) Tsugi no Itte Jikken kara no Kōsatsu" 将棋の認知科学的研究(2)次の一手実験からの考察 [A Cognitive Science Approach to Shogi Playing Processes (2)-Some Results on Next Move Test Experiments]. 情報処理学会論文誌 [Transactions of Information Processing Society of Japan] (in Japanese). Information Processing Society of Japan. 45 (5): 1481–1492. ISSN 0387-5806. 
  22. ^ Hosking 1997, p. 34, Part 1, Chapter 5: Introduction to Shogi Strategy and Tactics: "The pawn therefore has a vital role to play in both attack and defense. Having no pawn in hand (fugire), while one's opponent does have at least one pawn in hand, is clearly a disadvantange, and can be a very serious disadvantage."
  23. ^ Hosking 1997, p. 23, Part 1, Chapter 4: Comparison of Shogi with Chess.

Bibliography[edit]

Further reading[edit]

  • Aono, Teruichi (1983). Guide to shogi openings: Unlock the secrets of joseki 将棋定跡のカギ: 和英 定跡問題集. Translated by Fairbairn, John. 山海堂. ISBN 4-381-00598-8. 
  • Habu, Yoshiharu (2000). Habu's Words. Translated by Takahashi, Yamato; Hosking, Tony. The Shogi Foundation. ISBN 978-0-95310-892-3. 
  • Hodges, George, ed. (January 1976 – November 1987). "Shogi". Total of 70 bi-monthly issues published. The Shogi Association. 
  • Hosking, Tony (2006). Classic Shogi. The Shogi Foundation. ISBN 978-0-95310-893-0. 
  • Kitao, Madoka (2011). Joseki at a glance. Translated by Kawasaki, Tomohide. Nekomado. ISBN 978-4-9052-2501-0. 
  • Kitao, Madoka (2013). Sabaki at a glance. Translated by Kawasaki, Tomohide. Nekomado. ISBN 978-4-9052-2510-2. 
  • Kitao, Madoka (2014). Ending attack at a glance. Translated by Kawasaki, Tomohide. Nekomado. ISBN 978-4-9052-2513-3. 
  • Tanigawa, Koji (1988). Kōsoku no Shūbanjūtsu 光速の終盤術 [Lightning Speed Endgame Technique] (in Japanese). Japan Shogi Association. ISBN 978-4-81970-204-1. 
  • Yebisu, Miles (2016). Comprehensive shogi guide in English: How to play Japanese chess. Laboratory Publishing. 

External links[edit]