Smothered Mate: How the Knight Checkmates a Boxed-In King

What is a smothered mate?

A normal checkmate needs your pieces to cover every square around the enemy king. In a smothered mate, the defender does that job for you. The king's own rook, pawns and pieces sit on its escape squares, and a single knight delivers check.

It works because of how the knight moves. It jumps in an L shape over anything in its way, so its check cannot be blocked by putting a piece in between. The king has only two ways out: step to a free square, or capture the knight (itself or with another piece). If the king is boxed in and the knight is safe, the game is over.

The mate in one from the video

The position in the video is a real puzzle from our set (Lichess puzzle VSv2p, rated 883). Black is to play.

1. The setup move. Every puzzle starts with the opponent's move, played for you. Here a black rook on h2 is giving check, and the black knight on g4 defends it, so the white king cannot take it. White's only legal move is queen takes h2.
2. Look at the white king. It is on h1. Its rook is on g1, its pawn on g2, and now its own queen on h2. Every square around the king is full.
3. The knight jumps in. Knight from g4 to f2. Check. The king cannot move, the knight cannot be blocked, and no white piece can reach f2: the queen's path along the second rank is blocked by the g2 pawn. That is checkmate, Nf2#, the only mate in the position.

In the video the rook on h2 is already gone when the clip starts, because the game plays the setup move automatically. Try it yourself in the chess puzzles trainer.

Philidor's Legacy: the queen sacrifice that sets it up

Kings rarely box themselves in completely. Often the attacker has to force the last piece onto the escape square. The famous pattern is called Philidor's Legacy. Here is how it runs in several puzzles in our set, with Black attacking a white king on g1 and two black knights nearby:

1. Check into the corner. One knight checks from e2, and the king steps into the corner, h1.
2. Queen sacrifice. The queen checks on g1, right next to the king. The knight on e2 covers g1, so the king cannot take, and the rook takes the queen.
3. Smothered mate. Now the rook blocks g1, and the other knight jumps to f2. Mate.

In the textbook version a single knight does all the work, with a double check along the way, but the finish is the same: queen sacrifice, rook takes, knight mates.

Our puzzle set has 9 smothered mates that take three or four moves, rated from 2043 to 2303, and every one of them includes this queen sacrifice: the queen checks next to the cornered king and the rook takes it. In two of them the attacker also sacrifices a rook on h2 before the knight lands on f2.

How common is the smothered mate?

It is rare and memorable, which is why it shows up in so many puzzle collections. We counted the themes in all 3,000 puzzles NitroPlayer uses (from the Lichess puzzle database) and checked every mate in one with a chess move library:

Only 5 of those 270 are smothered mates, and only 14 of the 3,000 puzzles carry the smothered mate theme at all. The corner is not required, either: in 3 of the 5 one-move smothered mates the king stands on c1 or e1, boxed in after castling or before it.

How to find mate in one faster

• Start with the king, not your pieces. List its escape squares. If every one is filled by its own pieces, look for a knight check.
• Checks first. Go through every check you have, including captures that check. In a mate in one, the answer is always a check.
• Ask what the last move changed. In the video, the queen capture on h2 filled the king's last free square. Setup moves often do that.
• Look for queen checks next to the king. Most mates in one are queen mates, and a queen check right next to a king is often protected by another piece.
• Check the knight is safe. Before you play the knight check, make sure no piece can capture it.

Practice mate in one puzzles on NitroPlayer

• Themes, then Mate in 1: drills the 270 one-move mates, smothered ones included.
• Daily puzzle: one new puzzle every day, the same for every player, rated between 1000 and 1799.
• Hints: the first hint highlights the piece to move, the second shows the square. Any move that gives checkmate is accepted.
• Duel a friend: both of you get the same 20 puzzles and 3 minutes. A wrong move skips the puzzle and locks your board for 5 seconds.