Openings · 横歩取り△４五角
Side Pawn Bishop*45.
After Black takes the side pawn, trade bishops, throw a pawn in on 2h and drop the bishop on 4e, aiming to take on 6g and break in on 8h.
The idea
This line is White’s, and one of the sharpest of the Side Pawn Capture. You give up material for speed: bishops off, a pawn thrown in on 2h so that Black’s rook can no longer go back to 2h and guard 8h along the rank, then the bishop dropped on 4e, attacking the rook and threatening to take on 6g, and the rook breaking in on 8h.
The attack is old, ja.wikipedia says, and was revived in the late 1970s by Tanigawa Kōji, who twice won in 36 moves with it.
Research then showed that Black, defending exactly, comes out better: the rook to 2d, a bishop dropped on 7g that ignores the threat, the rooks traded, and a lance dropped on 3f. ja.wikipedia says it has almost vanished from professional play but is still common among amateurs with short time limits. The line here follows Black’s correct defence to the end.
Its first 29 moves are in several sources; the last five, from Black’s rook dropped on 8e, have one.
How it goes together
Both sides’ moves are shown, because this opening is an agreement rather than a system: one player cannot reach it alone, so a one-sided list of moves would be a fiction.
Step through the moves, or press play.
Tap a move to jump to it. Arrow keys work once the board has focus.
Every move of the line, with reasons
| # | Black | White | Why |
|---|---|---|---|
| 1 | ▲７六歩 7g7f | △３四歩 3c3d | Black opens the bishop’s diagonal. You open yours. |
| 3 | ▲２六歩 2g2f | △８四歩 8c8d | Black pushes the rook pawn. You push yours. |
| 5 | ▲２五歩 2f2e | △８五歩 8d8e | Black’s pawn to 2e. Yours to 8e. |
| 7 | ▲７八金 6i7h | △３二金 4a3b | Black’s gold to 7h guards the bishop’s head. Your gold to 3b guards yours. |
| 9 | ▲２四歩 2e2d | △同歩 2c2d | Black pushes the pawn on to 2d, to exchange it. You take. |
| 11 | ▲同飛 2h2d | △８六歩 8e8f | Black’s rook takes back. You exchange on your side too. |
| 13 | ▲同歩 8g8f | △同飛 8b8f | Black takes. Your rook takes back. |
| 15 | ▲３四飛 2d3d | △８八角成 2b8h+ | Black’s rook takes the side pawn on 3d. It now threatens to trade bishops on 2b, winning a gold or making a dragon. You trade bishops at once. |
| 17 | ▲同銀 7i8h | △２八歩 P*2h | Black takes back with the silver. A pawn dropped on 2h. Once the silver takes it, Black’s rook can no longer go back to 2h and guard 8h along the rank. |
| 19 | ▲同銀 3i2h | △４五角 B*4e | The silver takes. The opening’s move: a bishop dropped on 4e, at the rook, aiming to take on 6g and promote. |
| 21 | ▲２四飛 3d2d | △２三歩 P*2c | Black’s right answer: the rook to 2d, threatening to promote on 2a. A pawn dropped on 2c blocks it. |
| 23 | ▲７七角 B*7g | △８八飛成 8f8h+ | Black ignores the threat and drops a bishop on 7g, at your rook. Your rook takes the silver on 8h and promotes. |
| 25 | ▲同角 7g8h | △２四歩 2c2d | Black’s bishop takes the dragon. Your pawn takes Black’s rook on 2d: both rooks are gone. |
| 27 | ▲１一角成 8h1a+ | △３三桂 2a3c | Black’s bishop takes the lance on 1a and promotes. The knight jumps to 3c, where the gold guards it. |
| 29 | ▲３六香 L*3f | △同角 4e3f | A lance dropped on 3f, up the file at the knight. The sources call it the standard move. The bishop takes the lance: the strongest counter, one source says. |
| 31 | ▲同歩 3g3f | △５四香 L*5d | Black’s pawn takes back. A lance dropped on 5d, at the pawn on 5g. Black’s natural reply, a bishop dropped on 6f, loses. |
| 33 | ▲８五飛 R*8e | △４五桂 3c4e | Black’s right answer: a rook dropped on 8e. It stops your rook drop on 8h and threatens to take the knight on 8a. The knight jumps to 4e. |
| 35 | ▲同飛 8e4e | △５七香成 5d5g+ | Black’s rook takes it. The lance takes the pawn on 5g and promotes. |
| 37 | ▲５八歩 P*5h | Black drops a pawn on 5h, at the promoted lance. The horse on 1a covers 8h, and the source calls Black better. |
The plan once you are set up
- After Black’s rook takes the side pawn, trade bishops at once.
- Drop a pawn on 2h before the bishop drop.
- Drop the bishop on 4e, at the rook.
- Against the rook to 2d, guard with a pawn dropped on 2c before going for 6g.
- If Black trades rooks with the bishop on 7g, take the rook on 2d and get the knight out to 3c.
What to watch for
- The bishop drop without the pawn on 2h first. Black then pulls the rook back to 2h, guarding 8h along the rank, and the attack is gone.
- The rook to 3e against your bishop. Taking on 6g and then breaking in on 8h is good for you if Black plays naturally, the Japan Shogi Association’s column says, though newer analysis of a bishop dropped on 7g there gives Black a playable game.
- The rook to 2d and taking on 6g at once: Black promotes the rook on 2a and the attack runs out.
- After the lance on 3f, your bishop taking it and your lance dropped on 5d, the natural bishop drop on 6f loses, and the rook dropped on 8e is Black’s right answer. With your lance dropped on 5e instead, the same rook drop walks into your rook dropped on 2e, and the bishop drop on 6f is right.
What it is played against
Black runs the rook up to 2d, threatening to promote on 2a, then drops a bishop on 7g instead of retreating, trades rooks and promotes the bishop on 1a.
The lance dropped on 3f aims up the file at your knight on 3c; after your bishop takes it, the rook dropped on 8e stops your rook drop on 8h, and Black is better.
Play it against the bot.
The bot’s search levels, 9 to 12, open from a book that holds two of these openings, the Fourth File Rook and the Yagura; the Mino levels play the openings people play. Either way the review afterwards shows you where the game left the line. Try the line, then try the plan.