Subway Rook.

Static rook, against a ranging rook · castles into Paperweight · 地下鉄飛車 chikatetsu bisha

The idea

The Subway Rook attacks a ranging rook Anaguma where it is weakest, on its own edge, without breaking through the rest of White’s camp first. Black castles with the king on 7h, the silver on 8h and the golds on 6h and 5h, the long row of pieces called the Paperweight. The bishop goes to 6f and both knights jump, to 7g and 3g.

Once every piece between the lances has left the bottom rank, the rook drops to 2i, the lance steps up to 9h, and the rook slides along the empty rank to 9i, like a train in a tunnel.

The next step is the knight to 8e, with rook, bishop, knight and lance all aimed at 9c. ja.wikipedia notes that an Anaguma king has no way out, so the attack can sometimes mate at once; it also says the plan takes many moves and is not often played.

Black’s moves here are a Japan Shogi Association column’s build, in another order and without its push to 9e, which White’s edge pawn rules out. White’s moves come from one amateur online game, annotated by a blog whose author calls the moves up to the rook on 9i the expected course.

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

• Build the Boat: king to 7h, right gold to 5h, then push the edge pawn and the rook pawn to 2e.
• Bring the bishop to 6f, the left silver to 8h and the left knight to 7g.
• Push the pawn to 3f and jump the right knight to 3g, then lift the left gold to 6h.
• Drop the rook to 2i, lift the lance to 9h, and slide the rook to 9i.
• Attack the edge with the knight to 8e and the edge pawn.

What to watch for

• The knight jump to 4e. With the knight on 3g and White’s silver still on 4c, the blog’s author points out that it wins a dragon at once at move 29; White has to bring the silver out to 5d in time.
• White’s pawn to 6e against the bishop. Do not take it with the knight; retreat the bishop to 5g.
• A chance against a king still on 5a. A Japan Shogi Association column shows that once White has played the gold to 5b with the king still there, the bishop to 5g and the rook-pawn exchange break through.
• White’s silver to 6e. The blog shows White giving up a silver for the 7g knight and then dropping a knight on 6d, which makes the edge attack hard to start.

What it is played against

A Fourth File Rook castling in an Anaguma (ja.wikipedia adds the Right King in double static rook games).

White builds the Anaguma, then looks for play in the centre: the silver out to 5d, the pawn to 6d, and the silver to 6e to trade off Black’s attacking knight.

Black’s long build is the risk: the Anaguma side can change plans if Black shows the Subway too early.