The King That Castled Into a Discovered Check

Photo: TheBoburshokh / Wikimedia Commons (CC0)

Black has just castled queenside, putting the king on c8. Look at the white queen on e6 and the white knight on d7. The knight is standing on the line between the queen and the black king. What happens if the knight moves?

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Position after 31...O-O-O, with White to move. The knight on d7 stands between the queen on e6 and the black king on c8.

Analyze this position in the full game

Praggnanandhaa castled with 1 minute and 12 seconds left on his clock. It was the last mistake of a game he had been fighting uphill in for twenty moves.

Arjun Erigaisi 1-0 R Praggnanandhaa Tata Steel Chess Masters 2026, Wijk aan Zee · Round 1 White: Arjun Erigaisi (2775) · Black: R Praggnanandhaa (2758)

A sharp opening

The game began as a Queen's Gambit Accepted. Black took the c4 pawn, and then both sides pushed their centre pawns hard.

1.d4 d5 2.c4 dxc4 3.e4 e5 4.Nf3 exd4 5.Bxc4 Nc6 6.Qb3 Bb4+ 7.Nbd2 Qf6 8.O-O Nge7 9.e5 Qg6 10.Nh4 Qh5 11.Ndf3

For the first ten moves our own Stockfish 16 run, at depth 18, called the game level.

11...Ba5 12.h3 d3 13.Qxd3 Nxe5 14.Nxe5 Qxe5 15.Nf3 Qd6 16.Qb3

Black gave back the extra pawn with 12...d3, and after the trades White had quick development and pressure on f7. The engine rated White about one and a quarter pawns better after 16.Qb3.

The king that never castled

Black's king was still on e8. Its first choice here, according to our engine, was 16...O-O: castle, and get the king out of the centre.

16...Be6

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Position after 16...Be6, with White to move. The black king is still on e8, and White's bishop and queen both point toward the black kingside.

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Black blocked the bishop's line to f7 with the other bishop. But after the bishops were traded, Black had to take back with the f-pawn.

17.Bxe6 fxe6

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Position after 17...fxe6, with White to move. Black's pawn on e6 is on its own, and the black king is still in the centre.

Analyze this position in the full game

Now the pawn on e6 had no pawn beside it on the d-file or the f-file to protect it. Our engine rated White about three and a half pawns better. A king stuck in the middle and a weak pawn in front of it is a hard combination to defend.

18.Rd1 Qb6 19.Qa4+ c6 20.Qe4 Qb5 21.Qxe6

White won the e6 pawn. White kept bringing pieces toward the black king, and the black king stayed on e8.

21...Qf5 22.Qe2 Rf8 23.Rd3 Bb6 24.Bg5 Rf7 25.g4 Qg6 26.Re1 Bxf2+ 27.Kxf2 Qxg5 28.Kg2 Qc5 29.Ne5 Rf4 30.Nd7 Qg5 31.Qe6

The move that ended it

31...O-O-O

Castling at last. But now go back to the first diagram. The knight on d7 is blocking the queen on e6 from the black king on c8. If the knight moves anywhere, the queen gives check. This is called a discovered check: one piece moves out of the way, and the piece behind it gives check.

32.Nf6+

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Position after 32.Nf6+, with Black to move. The queen on e6 gives check along the diagonal to c8. Black has three legal moves: Kb8, Kc7 and Rd7.

Analyze this position in the full game

The knight's jump also cleared the d-file. The white rook on d3 now attacks the black rook on d8, and only the king defends it. Black has three legal moves, and our engine finds a forced checkmate for White after every one of them. Praggnanandhaa resigned.

What this game teaches

1. Castle early. Black's king stayed on e8 until move 31. The engine's choice on move 16 was simply to castle.

2. An isolated pawn in front of your king is a target. After 17...fxe6, the pawn on e6 could not be protected by another pawn, and White won it on move 21.

3. Look for pieces standing on a line to the king. When one of your pieces stands between your queen, rook or bishop and the enemy king, moving it gives a discovered check.

4. Check your king's new square before you castle. 31...O-O-O put the king on c8, right on the diagonal the white queen was waiting on.

5. The clock matters most when you are already under pressure. Praggnanandhaa had just over a minute for his last moves before move 40, while defending a difficult position.