The "smothered mate" occurs in cases where a king is too well defended for its own good. The ingredients are simple; a king (usually in the corner of the board) which is completely entombed by his own pieces, is attacked by a knight which can jump over the defenders to threaten the king. Because the king has nowhere to run, the result is a checkmate.
Typically, a smothered mate requires a sacrifice and a series of checks to force the opponent trap his own king, but this example requires just one move to complete. In the diagram above, White's king is already stuck on h1, as his own pieces prevent him from moving anywhere. For Black, it's just a matter of moving the knight to the right square. In this case, the proper move is Nf2++, delivering a smothered mate.
