Tsukada Special (塚田スペシャル tsukada supesharu) is a Floating Rook variant of the Double Wing Attack shogi opening developed by professional Yasuaki Tsukada in the 1980s.
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The strategy is characterized by an aggressive offense at a very early stage of the game and a particular positioning of Black's rook on 2d after a pawn exchange initiated by Black dropping a pawn on 2d.
According to Kiyokazu Katsumata, the Tsukada Special has been influential on many different openings, especially the Twisting Rook opening as well as Ranging Rook strategies.
Initial positioning
6. R-2f .... After the main opening lines of Double Wing Attack Floating Rook, Black floats their rook to 2f temporarily preventing White from exchanging pawns on the eighth file.
6. ... S-7b/S-6b. White now has a major choice of whether to move their right silver to either 7b or 6b. The 7b option is the newer joseki position. Staying on the seventh file (S-7b) allows White the options of playing either Climbing Silver (advancing down the eighth file) or Reclining Silver (advancing to the central file) while moving the silver to the sixth file (S-6b) favors Reclining Silver since White's Climbing Silver will be slower (due to the pawn blocking advancement at 6c). Another difference is that S-7b does not block the king from moving to 6b and 7a, which may be an important escape route if Black is able to penetrate White's camp before White can castle. However, with the S-7b move, White's pawn in front of the king at 5c remains undefended in contrast with the S-6b move. In the diagram and the immediately following discussion, S-7b is shown.
7. P-1f. After White's choice of their silver movement, Black advances their edge pawn on the first file. Moving Black's edge pawn allows the lance to be free to move to 1g in order for it to be defended by the knight on 2i, which may be beneficial if White can drop a bishop on an undefended 2h square. Additionally, the open 1g square allows the knight a place to flee from a pawn drop by White at 2h. And, if Black's rook can reach the 2d square, then an edge attack with the first file pawn, a dropped pawn, and the lance may be possible.
7. ... P-1d. White mirrors Black's edge pawn so that their bishop can move to 1c, which allows (i) defense of 2d from Black's rook, (ii) a possible attack on 5g, (iii) an escape route in case White's camp along the second file is broken, and (iv) prevents Black's knight from attacking White's lance if positioned on 1c after Black's pawn drop on 1c since the lance can move forward to 1d. The advanced pawn also prevents Black's pawn from further encroachment on the first file.
8. P-3h. Black then advances their silver on the third file. This position has the same benefits as White's S-7b choice and defends the 2g square from any future bishop drop on that square by White.
8. ... P-6d. White moves their sixth file pawn allowing an opening for the Reclining Silver position (which is S-5d).
9. P-7f. Black responds by opening their bishop diagonal.
9. ... P-8f. Once Black's bishop diagonal is open, the advanced pawn now prevents Black's rook from defending the f rank. This allows White to initiate a pawn exchange on the eighth file by attacking the head of Black's bishop.
10. Px8f Rx8f. Pawn exchange via White's rook.
11. P*2d. Black drops a pawn to attack the bishop's head again for another pawn exchange. This is an essential characteristic of the Tsukada Special.
11. ... Px2d 12. Rx2d. After the Tsukada Special pawn exchange, Black's rook is in positioned on the d rank. From here, Black may have the possibility to start an edge attack on the first file or possibly capture White's floating pawn on 6d.
Opening White's bishop diagonal (8. ... P-3d)
8. ... P-3d. 9. P-7f ... . If White chooses to open their bishop's diagonal (P-3d) instead of preparing for Reclining Silver (P-6d) at move 16, then Black can also open their bishop's diagonal.
9. ... P-8f. 10. Px8f Rx8f. White exchanges pawns on the eighth file.
11. P*2d Px2d 12. Rx2d ... . Black initiates the Tsukada Special pawn exchange. And, after the pawn exchanges on both sides, the board can reach a position that resembles the Side Pawn Capture opening.
At this point, there are also a number of move missteps that White is at risk of making that lead to stronger positions for Black including even some forced checkmate traps.
Checkmate sequence 12. ... R-8d
12. ... R-8d. For example, if White had moved their silver to the sixth file on move 12 (that is, 6. ... S-6b) and at move 24 reacts to Black's rook on 2d by moving their rook to 8d to protect the side pawn at 3d, a series of moves will lead to a checkmate by Black.
13. Bx22+ Sx22. 14. B*6f .... Black can trade the bishops and then drop their bishop to 6f attacking both White's rook and silver.
14. ... Rx9i+. 15. Bx22+ .... White's rook can capture Black's knight and promote while Black can capture White's silver.
15. ... Gx22. 16. Rx22+ .... White's gold captures the bishop, but Black recaptures with their rook and promotes.
16. ... +Rx7i. 17. G*6i .... If White's rook captures Black's silver checking their king, Black can block White's rook by dropping a gold between the rook and king.
17. ... G*6i. +Rx9i. White's rook can escape and capture Black's lance.
18. S*4b K-5b. 19. S-3a= .... But then, Black starts the forced checkmate by dropping a silver on the fourth file checking White's king. The king retreats to the b rank, but the silver can move to the third file unpromoted leaving Black's dragon to check the king. No matter whether the king moves to the a rank or another piece is dropped, Black's dragon checkmates via the fourth file (+R-4b) in the next move.
Note that if White had played S-7b earlier in the opening (instead of S-6b), then their king would have had an escape route from this particular checking sequence.