Tesuji · 飛角の手筋
The two sliding pieces win material by attacking two things at once, and win games by being far away from the fight until the moment they are not.
Most of a rook’s or bishop’s techniques are forks: the pieces reach so far that two targets on one line, or one on each of two lines, are common. The rest are about distance, keeping the piece out of reach of pawns while it still commands the squares it needs.
What. A rook dropped or moved to a square from which it attacks one piece along the rank and another along the file.
Why. The rook’s two lines make a cross; a piece at the end of each arm is a fork nothing can answer.
When. Scan for two undefended enemy pieces that share neither rank nor file; the square where their rank and file meet is the cross rook’s square, if it is empty and safe.
What. A move that gives check and attacks the enemy rook at the same time, most often a bishop move or drop that hits both along its two diagonals.
Why. The check must be answered, so the rook is lost. It is the most common way a rook is won in amateur games, and the reason the proverb says never to keep king and rook close.
When. Whenever the king and the rook stand on the two diagonals through one empty square, and the square is safe for a bishop for one move.
What. The dragon placed two squares from the king in a straight line, with one empty square between them.
Why. The king cannot approach, anything dropped between is pinned, and the dragon covers the whole rank or file behind the king. With one general in hand it is usually mate.
When. Whenever the dragon can reach that square without being captured. See the worked problem on the mating patterns page.
What. A bishop dropped in your own camp or the far corner of the board, on a long diagonal that ends in the enemy king’s castle.
Why. From that distance no pawn can chase it, and the diagonal it controls is the one the defender cannot block without weakening the castle. The proverb says drop the major pieces at a distance.
When. When a bishop in hand has no safe square near the king. Look for the long diagonal instead; it is often stronger than the close attack.
What. Pushing the pawn in front of your rook until it exchanges with the enemy pawn, then recapturing with the rook and retreating.
Why. Three gains, as the teaching goes: a pawn in hand, an open file for the rook, and a rook that has been to the enemy camp and back for free. Most static rook openings begin with this exchange.
When. Early, when the enemy bishop or silver does not yet guard the square. The whole opening theory of the static rook is about when this exchange is allowed.
What. Bringing the promoted bishop back beside your own king rather than keeping it in the attack.
Why. A horse steps one square in every direction and slides along diagonals: it covers the squares around the king better than any general and can still strike out. The proverb pairs it with the dragon: dragon in the enemy camp, horse in your own.
When. When the opponent’s attack is beginning and your bishop has just promoted. Bring it home first; the attack will still be there.
The app’s review marks the moment a game turned and says what was better. Often the better move is one of these.