Smothered mate
A smothered mate is a knight checkmate against a king hemmed in by its own men: every square the king could use holds its own pieces, and a knight check cannot be blocked.
This is the one mate where the victim's own army does the work. The king sits in a corner, ringed by a rook and pawns that were meant to guard it, and a knight arrives with check. Only a knight can do it, because a knight's check cannot be blocked and the king has no way to capture a piece it cannot reach.
The textbook route to the position is a sacrifice. Imagine a black king on h8 with a rook on f8 and pawns on g7 and h7. White gives up the queen with Qg8+, the rook is forced to capture on g8, and the knight on e5 then jumps to f7 with mate. The queen sacrifice drags the rook onto the one square that finishes the smother.
When looking for it, check three things: is the king in a corner or against an edge, are all its neighbors occupied by friendly pieces, and can a knight reach a square attacking the king? Then see whether a sacrifice can force the last neighbor into place.
To avoid it, make luft so the king is not walled in, and be careful when an enemy knight is within two jumps of your king's corner. Before you capture an offered queen, check where your capturing piece goes and what it blocks.
In the diagram it is Black's move. The knight on d3 jumps to f2, giving check to the king on h1. The rook on g1 and the pawns on g2 and h2 fill every other square.
Compare it with Anastasia's mate. Anastasia's mate is a checkmate in which a knight and a rook trap a king on the edge, with the king's own pawn blocking its escape and the rook checking along the edge file.
Compare it with Arabian mate. An Arabian mate is a corner checkmate where a rook gives the check from beside the king, and a knight, a jump away from the rook, guards it and covers the one flight square the rook leaves open.
A neighboring idea is Blackburne's mate. Blackburne's mate is a checkmate made with two bishops and a knight, where a bishop checks on h7 guarded by a knight on g5 while the other bishop on the long diagonal covers g7 and h8.
Knowing "Smothered mate" helps most once you can spot it in a real game. A first lesson with George Li starts from your own games and finds the tactics you keep missing.
Related terms
Checkmate, or mate, ends a chess game at once: the king of the side to move is under attack, and none of that side's legal moves can remove the attack, so the player who delivered it wins.
A knight fork is a move that places a knight on a square from which it attacks two or more enemy pieces at once, so the opponent cannot save them all.
A queen sacrifice gives up the strongest piece on the board, usually with a check or a capture, to win through a forced checkmate or to gain enough other material to be clearly ahead.
A mating net is a setup in which the enemy king is surrounded by attackers and its own pieces so tightly that checkmate cannot be avoided, even if the final blow is a move or two away.
A back rank mate is a checkmate on a player's first or eighth rank, typically by a rook or queen, delivered when the king's own pawns leave it no square to step to.
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