Wrong Diagonal Bishop

The Wrong Diagonal Bishop or Parallel-Diagonal Bishop (筋違い角 or 筋違角 sujichigai kaku) is a shogi opening characterized by a bishop trade followed by dropping the bishop in hand on the 45 square if played by Black or the 65 square if played by White.

Wrong Diagonal Bishop
☖ pieces in hand: 角
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香桂銀金王金 桂香1
 飛     銀 2
歩歩歩歩歩歩 歩歩3
      歩  4
     角   5
  歩      6
歩歩 歩歩歩歩歩歩7
       飛 8
香桂銀金玉金銀桂香9
☗ pieces in hand: –

Introduction

The Wrong Diagonal Bishop opening is one of the oldest shogi openings appearing around the same time as the Black's Static Rook vs White's Traditional Ranging Rook type of openings (thus predating other old openings such as Fortress, etc). The Wrong Diagonal Bishop frequently appears in the recorded handicap games from the Edo period.

The name comes from the bishop being only able to move to squares that are not available from the bishop's start position – thus, the wrong diagonal.

The main point of dropping the bishop is to fork two opponent pawns. Since the opponent is most likely to defend the pawn in their camp, the player can get a material advantage of one pawn. Furthermore, adopting such an early attack can put pressure on their opponent and disturb their normal development in other openings.

After the bishop drop and pawn capture, the player must then contend with whether they will retreat their bishop to the left or right side.

There are two main types of Wrong Diagonal Bishop openings. One variation stems from the Bishop Exchange opening, which is a Double Static Rook opening where both players advance their rook pawns and develop their left silvers to prevent each other from trading off their rook pawns. Here the Wrong Diagonal Bishop drop occurs immediately after the bishop trade off.

The other variation – Primitive Wrong Diagonal Bishop (原始筋違い角) – has a very early bishop trade off and subsequent bishop drop. This occurs directly after the players' bishop diagonals are opened after the third move (or the fourth move if played by White). This set of variations leads to more unusual formations in which either player could play alternately a Static Rook or Ranging Rook position. Unlike the first Bishop Exchange variation, this Primitive variation has Black losing tempo.

Primitive Wrong Diagonal Bishop

One of the aims of Primitive Wrong Diagonal Bishop as played by Black is to make it difficult for White to play a standard Ranging Rook strategy as in order to do White's rook must be moved twice (first to the sixth file, then to the fourth file) losing tempo. Otherwise, a Ranging Rook player must spend several moves developing their generals in order to keep their line of pawns defended while also clearing a path on rank 2 for the rook to be swung over to a Ranging Rook file. Needless to say, this second option often leaves White with more limited castle options.

Black's variations

After Black's bishop drop, White has several options to defend their central pawn. Three are listed here. Other options are listed in the Double Wrong Diagonal Bishop section below.

Takeichi variation

The Takeichi Wrong Diagonal Bishop (武市流 takeichi-ryū) is a variation developed by Saburō Takeichi (武市三郎).

Double Wrong Diagonal Bishop

There are three main variations of Double Wrong Diagonal Bishop.[1]

Takeichi vs Senzaki 1990
☖ pieces in hand: 歩
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香桂銀 王  桂香1
 飛  金 金  2
歩歩歩歩歩歩銀歩歩3
         4
         5
  角 角    6
歩歩 歩歩歩歩歩歩7
 飛 銀     8
香桂 金玉金銀桂香9
☗ pieces in hand: 歩

The Double Wrong Diagonal Bishop B*65 variation appears in the Saburō Takeichi vs Manabu Senzaki Meijin ranking tournament on 1990 June 18.[2] After rejecting a bishop trade, Senzaki also captured Takeichi's pawn on the seventh file. Takeichi played an Opposing Rook position with his bishop on the central file.

Black's Wrong Diagonal Bishop after White's bishop exchange
Uncommon Variant for Black
☖ pieces in hand: –
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香桂銀金王金 桂香1
 飛     銀 2
歩歩歩歩歩歩 歩歩3
      歩  4
     角   5
  歩    歩 6
歩歩 歩歩歩歩 歩7
 銀     飛 8
香桂 金玉金銀桂香9
☗ pieces in hand: –

It's also possible to play a Wrong Bishop Diagonal opening if White trades off the bishops first. This opening was played by Ryō Shimamoto against Hiroshi Kobayashi in 2016.[3] Presumably, Kobayashi made the bishop trade in order to play a Tempo Loss Bishop Exchange opening. However, Shimamoto foiled Kobayashi's preparation by dropping the bishop to 45 after Kobayashi moved his silver up to 22. This move sequence was 1. P-76 P-34 2. P-26 Bx88+ 3. Sx88 S-22 4. B*45.

White's variations
Black Plays Static Rook
☖ pieces in hand: –
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香桂銀金王金銀桂香1
 飛     角 2
歩歩歩歩歩歩歩歩3
      歩  4
         5
  歩    歩 6
歩歩歩歩歩歩歩7
 角     飛 8
香桂銀金玉金銀桂香9
☗ pieces in hand: –
1. P-76 P-34
2. P-26

Bishop trade by White
Central pawn push variation
☖ pieces in hand: 歩
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香桂銀金王金桂香1
 飛     銀 2
歩歩歩歩歩歩 歩歩3
      歩  4
         5
  角 歩  歩 6
歩歩 歩歩歩 歩7
 銀  金銀 飛 8
香桂 金玉 桂香9
☗ pieces in hand: 角
Rook pawn push, Opposing Rook variation
☗P-25
☖ pieces in hand: 歩
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香桂銀金王金銀桂香1
 飛 2
歩歩歩歩歩歩 歩歩3
      歩  4
       歩 5
  角     6
歩歩 歩歩歩歩 歩7
 銀  金  飛 8
香桂 金玉 銀桂香9
☗ pieces in hand: 角

Bishop trade by Black

This is a variation introduced by professional shogi player Takeshi Ōwaku (大和久彪) in 1937.[4] In contrast to the above, White encourages Black to make the bishop trade instead, which results in White not losing tempo.

Ōwaku variation
☖ pieces in hand: 歩
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香桂銀金王 銀桂香1
 飛       2
歩歩歩歩歩歩金歩歩3
      歩  4
      歩 5
  角      6
歩歩 歩歩歩歩 歩7
 銀    銀飛 8
香桂 金玉金桂香9
☗ pieces in hand: 角
6. S-38 Bx76

Wrong Diagonal Bishop Bishop Exchange
Bishop Exchange variation
☖ pieces in hand: 角
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香桂銀金王  桂香1
 飛    金銀 2
歩 歩歩歩歩 歩歩3
      歩  4
 歩   角 歩 5
  歩      6
歩歩銀歩歩歩歩 歩7
       飛 8
香桂 金玉金銀桂香9
☗ pieces in hand: –
Main article: Bishop Exchange, Wrong Diagonal Bishop

The Wrong Diagonal Bishop variation of the Bishop Exchange opening was most popular during the 1950s and was often played by Yasuharu Ōyama and Masao Tsukada.[4]

Unlike the Primitive variations discussed in the earlier sections, the Bishop Exchange variation proceeds like all other Bishop Exchange variations until just after White trades off the bishops. It is at this point that the bishop in hand can be dropped to the wrong diagonal.

Thus, this opening is quite different from the Primitive Wrong Diagonal Bishop in that there is much more piece development preceding the bishop drop. Also, the Wrong Diagonal bishop drop can only be made by Black since Black's pawn on 76 is already defended by the silver on the 77 square, which, needless to say, eliminates the possibility of Double Wrong Diagonal Bishop variations.

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See also

References
  1. (武市 2003: chap. 3)
  2. "武市三郎 vs. 先崎学 順位戦". Shogidb2.com. Retrieved 27 August 2018.
  3. https://shogidb2.com/games/1bf3a619fc8463e9556f2faf39fd01a9b3216ac0
  4. Fairbairn (1980)

Bibliography
  • Fairbairn, John (1980). "The wrong-diagonal bishop". Shogi (23): 18.
  • Hodges, George, ed. (1977). "Shogi openings". Shogi (10): 9, 12–13.
  • Hodges, George (ed.). "The wrong diagonal 角 part one". Shogi (57): 6–8.
  • Hodges, George, ed. (1986). Translated by Murphy, David. "The wrong diagonal 角 part four". Shogi (60): 13–15.
  • Hodges, George, ed. (1986). "The wrong diagonal 角 part five". Shogi (61): 16–17, 7.
  • Hodges, George, ed. (1986). Translated by Murphy, David. "The wrong diagonal 角 part six". Shogi (62): 13–14, 16.
  • Hosking, Tony (1996). The art of shogi. The Shogi Foundation. ISBN 978-0-95310-890-9.CS1 maint: ref=harv (link)
  • Kimura, Yoshio (1986). "The wrong diagonal 角 part seven". Shogi (63): 6–7.
  • Kitao, Madoka (2011). Joseki at a glance. Translated by Kawasaki, Tomohide. Nekomado. ISBN 978-4-9052-2501-0.
  • Naito, Kunio (1985). Translated by Fairbairn, John. "The wrong diagonal 角 part two". Shogi (58): 7–9.
  • Naito, Kunio (1986). Translated by Murphy, David. "The wrong diagonal 角 part three". Shogi (59): 15–17.
  • 武市 [Takeichi], 三郎 [Saburō] (2003). 武市流力戦筋違い角の極意. 毎日コミュニケーションズ. ISBN 4-8399-1093-6.
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