Crab Silvers.

Static rook, a rapid attack on the Yagura · none (the king and golds never move) · カニカニ銀 kanikani-gin

The idea

Crab Silvers is Kodama Kōichi’s rapid attack against a Yagura, named for the two silvers that stand out on 6f and 4f like a crab’s claws. It won the 30th Masuda Kōzō Award, announced in 2003. Black never castles: the king and both golds stay where they started, which keeps the camp sound against a rook exchange.

On move 5 the left silver goes on to 7g instead of the usual pawn to 6f, and the rook pawn goes to 2e so that White has to close the bishop’s diagonal with the silver on 3c. The right silver goes 4h, 5g, 4f. When White has pushed the centre pawn, the rook moves to the centre, the bishop goes out to 9g and the knight jumps to 7g, and Black breaks with the pawn to 5e.

Two sources give the first 27 moves; the break has one, which says Black has already won the opening at move 27 and calls the end winning for Black. ja.wikipedia files the opening with the Yagura, and some count it among the surprise openings.

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.

The plan once you are set up

• Open the diagonal, bring the left silver to 6h and 7g, push the centre pawn, put the right silver on 4h, then push the rook pawn to 2e.
• After White’s silver closes the bishop’s diagonal on 3c, take the right silver up through 5g to 4f.
• Push the edge pawn to 9f, put the bishop on 9g and the left silver on 6f.
• Swing the rook to 5h and jump the knight to 7g.
• Break with the pawn to 5e, then bring the knight in to 6e.

What to watch for

• The pawn to 3f. ja.wikipedia says that when the attack comes through the centre, pushing the 3rd-file pawn weakens your own king and slows the attack.
• White’s prepared centre: the right gold to 5b, then the rook to 6b. The section below shows the attack still breaking through, with the knight brought in before the silver takes.
• White keeping the centre pawn back. Then the centre gives no point of contact; ja.wikipedia’s answer is the bishop pulled back to 7i and the right silver used as a Rushing Silver on the 3rd file.
• Your king. Nothing guards it but the golds on the bottom rank; the attack has to keep going.

What it is played against

White heads for a Yagura with the silver on 3c and the golds on 3b and 4c. At first White let Black build the formation with a plain gold to 3b; later White prepared the centre with the right gold to 5b and kept the rook ready to defend the 6th file.

When White prepares the centre

Against the right gold to 5b (金右型)

ja.wikipedia says White at first let Black build the formation against a gold on 3b, then came to prepare the centre with the right gold to 5b instead, because the central break was hard to stop.

The source of the line above gives that defence too, taken as far as it goes: the gold on 5b and then 4c, the silver on 5c and the pawn on 6d (the first board), and then the rook moved to 6b as well. Black still breaks through.

The silvers stand on 4f and 6f as before, but this time the pawn to 5e comes first, the knight jumps to 7g only after White has taken, and the left silver takes on 5e. When White drops a pawn on 5d, the knight is given up on 6e, the silver takes the pawn on 5d, and when White’s gold takes the silver, the rook takes the gold (the second board).

The source says White’s camp is broken.