A smothered mate is the knight's signature checkmate: the enemy king is completely boxed in by its own pieces, so a single knight check, which nothing can block, ends the game on the spot. It's the only mate in chess that one lone knight can deliver.
The pattern to memorize: king in the corner, its own rook and pawns filling every escape square, and your knight landing on the one square that checks the corner. Castled kings that keep a rook parked next to them are the classic victims, and it's why "give your king an escape square" is real advice, not just a proverb.
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Black's king on h8 is sealed in by its own rook on g8 and pawns on g7 and h7. White's knight is one jump away.
Deliver checkmate in one move.
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