Bishop and knight checkmate
The bishop and knight checkmate in chess is the checkmate of a lone king which can be forced by a bishop, knight, and king. With the stronger side to move and with perfect play, checkmate can be forced in at most thirty-three moves from any starting position where the defender cannot quickly win one of the pieces. The exceptions occur when (1) The defending king may be forking the bishop and knight so that one of them is lost on the next move, or (2) the knight may be trapped in a corner by the defending king and the knight is lost in one or two moves, and the position is not in the ""stalemate trap"" (see below). These exceptions constitute about 0.5% of the positions. Checkmate can be forced only with the defending king in a corner controlled by the bishop or on a square on the edge next to such a corner. Although this is classified as one of the four basic or elementary checkmates (Fine & Benko 2003:1) (the others being king and queen; king and rook; or king and two bishops against a lone king), it occurs in practice approximately only once in every 6000 games.