Castles · 二枚金
Static Rook Gold Twins.
The Boat castle with the 6i gold stepped up to 6h, so two golds stand side by side next to the king.
How it goes together
Build the Boat castle: king 7h, bishop 8h, the right gold on 5h, the left gold and the left silver still on 6i and 7i. Then the 6i gold steps straight up to 6h. The two golds now stand side by side on 6h and 5h and guard each other, with the king beside them. The 7i silver stays where it started, under the king. It guards the 6h gold, and it guards 8h, so if the bishops are traded there the silver can take back instead of the king.
This castle is a Boat and one more move: the first seven below build the Boat, and the gold steps up last.
Move by move
Black only, from the start position: the Boat castle’s seven moves, then one more.
Step through the moves, or press play.
Tap a move to jump to it. Arrow keys work once the board has focus.
Eight moves. The last one is the whole difference from the Boat: the gold the Boat left on 6i steps up to 6h, next to its partner. ja.wikipedia quotes Nakahara Makoto, who rebuilt a Boat this way in 1975: with the gold, the castle is complete in one move, where moving the silver up would need a gold move later.
What it is good against
The bishop trade. In a Boat whose left silver has left 7i, with the rook up on 2f, a bishop trade on 8h is awkward: the king has to take back, and a bishop dropped on 4d then checks it and hits the rook at once. Here the left silver stays on 7i and takes back instead, so the rook can go to 2f and the right knight can join in, the rook, bishop, silver and knight that ja.wikipedia calls an ideal attacking formation. If the game turns slow it can still become a Matsuo Anaguma (ja.wikipedia).
Where it breaks
It is the Gold Twins turned round, with the bishop’s head left weak (shogi-gym). It also keeps the Boat family’s weak square: ja.wikipedia says every form of the Boat is weak at 8g.
When to build it
A static rook against a ranging rook, for a rapid attack, with the right silver on 5g, the right knight on 3g and the rook lifted to 2f. Computer programs rated it highly, and Ōhashi Takahiro’s results with it made it popular among young professionals; Shoshi Kazuharu wrote a book on it in 2020 (Mynavi). The shape is old: ja.wikipedia shows it in a 1935 game and in a 1958 NHK Cup game between Hanamura Motoji and Masuda Kōzō. For the ranging rook’s castle of the same name, see the Gold Twins.
Build it at the board.
The app’s lesson walks the king into a Mino one step at a time, and its review names the castle you were building when a game turned.