Checkmate (frequently shortened to mate) is a situation in chess (and in other boardgames of the chaturanga family) in which one player's king is threatened with capture (in check) and there is no way to meet that threat. Delivering checkmate is the ultimate goal in chess: a player who is checkmated loses the game (the king is never actually captured – the game ends as soon as the king is checkmated). In practice, most players resign an inevitably lost game before being checkmated.
If a king is under attack but the threat can be met, then the king is said to be in check, but is not in checkmate. If a player is not in check but has no legal move (that is, no valid move that would not put the king in check), the result of the game is stalemate, and the game ends in a draw. (See Rules of chess.)
Moghadam traced the etymology of the word mate. It comes from a Persian verb mandan, meaning "to remain", which is cognate with the Latin word manco. It means "remained" in the sense of "abandoned" and the formal translation is "surprised", in the military sense of "ambushed" (not in the sense of "astonished"). So the king is in mate when he is ambushed, at a loss, or abandoned to his fate.
The term checkmate has come to mean in modern parlance an irrefutable and strategic victory.
In the first diagram, White checkmates easily by forcing the black king to the edge a rank at a time or a file at a time:
Checkmate can be forced even away from the edge of the board with two rooks and a king, or with a queen, rook, and king, while two queens are able to force checkmate in the center without the help of the king.
The checkmate with the queen is the most important, but it is also very easy to achieve. It often occurs after a pawn has queened. The next most important one is the checkmate with the rook, and it is also very easy to achieve. The checkmates with the two bishops and with a bishop and knight are not nearly as important, since they only occur infrequently. The two bishop checkmate is fairly easy to accomplish, but the bishop and knight checkmate is difficult and requires precision.
With the side with the queen to move, checkmate can be forced in at most ten moves from any starting position, with optimal play by both sides, but usually fewer moves are required. . In positions in which a pawn has just promoted to a queen, at most nine moves are required . In this position, White checkmates by confining the black king to a rectangle and shrinking the rectangle to force the king to the edge of the board:
The superior side must be careful to not stalemate the opposing king, whereas the defender would like to get into such a position. There are two general types of stalemate positions that can occur, which the winning side must avoid .
With the side with the rook to move, checkmate can be forced in at most sixteen moves from any starting position . Again, see Chess/The Endgame for a demonstration of how the king and rook versus king mate is achieved.
In this position, White checkmates by confining the black king to a rectangle and shrinking the rectangle to force the king to the edge of the board:
There are two stalemate positions to watch out for: :
It is not too difficult for two bishops to force checkmate, with the aid of their king. Two principles apply:
In the position from Seirawan, White wins by first forcing the black king to the side of the board, then to a corner, and then checkmates. It can be any side of the board and any corner. The process is:
Note that this is not the shortest forced checkmate from this position. Müller and Lamprecht give a fifteen move solution, however it contains an inaccurate move by Black (according to endgame tablebases) . With optimal play by both sides, checkmate in this position requires seventeen moves. The longer variation is more instructive.
Here are the two basic checkmate positions with a bishop and a knight, or the bishop and knight checkmate. The first position is a checkmate by the bishop, with the king in the corner. The second position is a checkmate by the knight, with the king in a side square next to the corner. Alternatively, the knight can be on c6 or d7 in the second position.
With the side with the bishop and knight to move, checkmate can be forced in at most thirty-three moves from any starting position , except those in which the defending king is initially forking the bishop and knight and it is not possible to defend both. However, the mating process requires accurate play, since a few errors could result in a draw either by the fifty move rule or stalemate.
Opinions differ as to whether or not or not a player should learn this checkmate procedure. James Howell omits the checkmate with two bishops in his book because it rarely occurs but includes the bishop and knight checkmate. Howell says that he has had it three times (always on the defending side) and that it occurs more often than the checkmate with two bishops . On the other hand, Jeremy Silman includes the checkmate with two bishops but not the bishop plus knight checkmate because he has had it only once and his friend John Watson has never had it . Silman says
...mastering it would take a significant chunk of time. Should the chess hopeful really spend many of his precious hours he's put aside for chess study learning an endgame he will achieve (at most) only once or twice in his lifetime?"
In the third diagram, White can play 1. Nc6+ Ka8, but now if White plays 2. Nb5 threatening 3. Nc7#, Black is stalemated. It is sometimes possible to force checkmate with two knights against a pawn, because in some positions, having a pawn removes this stalemate defence.
Three knights and a king can force checkmate against a lone king within twenty moves . These situations are generally only seen in chess problems, since one or more of the knights must be a promoted piece, and there is very rarely a reason (e.g., avoidance of stalemate) to promote a pawn to anything other than a queen (see underpromotion).
Under some circumstances, two knights and a king can force checkmate against a king and pawn (or rarely more pawns). The winning plan, quite difficult to execute in practice, is to blockade the enemy pawn(s) with one of the knights, maneuver the enemy king into a stalemated position, then bring the other knight over to checkmate. (See Two knights endgame.)
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