Sacrifice (chess)

In the game of chess, a sacrifice is a move giving up a piece or pawn in the hopes of gaining tactical or positional compensation in other forms. A sacrifice could also be a deliberate exchange of a chess piece of higher value for an opponent's piece of lower value.

Any chess piece except the king can be sacrificed. Because players usually try to hold onto their own pieces, offering a sacrifice can come as an unpleasant surprise to one's opponent, putting him off balance, and causing him to waste much precious time trying to calculate whether the sacrifice is sound or not and whether to accept it. Sacrificing one's queen, or a string of pieces, adds to the surprise, and such games can be awarded brilliancy prizes.

Types of sacrifice

True vs. Pseudo

Sacrifices can either be true sacrifices or pseudo sacrifices:

*In a true sacrifice, the sacrificing player will often have to play on with less material than his opponent for quite some time.

*In a pseudo sacrifice, the player offering the sacrifice will soon regain the sacrificed material, or he may even gain more material than was originally sacrificed. A pseudo sacrice of this latter type is sometimes known as a sham sacrifice, and will often lead to mate.

Because a true sacrifice produces less direct results, it may not even be clear even after several moves that the chances of the player who offered the sacrifice are any better than they were before the sacrifice was initiated. Because of this, true sacrifices are also called speculative sacrifices.

True sacrifices

Attack on the king. A player might sacrifice a pawn or piece to get open lines around the vicinity of the opponent's king, to get a kingside space advantage, to destroy or damage the opposing king's pawn cover, or to keep the opposing king in the center. However, the path to checkmate might not be clear, and one might not exist. If the opponent fends off the attack while managing to keep the material, they will usually win the game. The Greek gift sacrifice is a canonical example. Development. It is common to give up a pawn in the opening to speed up one's development. Gambits typically fall into this category. Developing sacrifices are frequently returned at some point by the opponent, else the development edge might be leveraged to create more substantial threat such as a kingside attack.

Strategic/positional. In a general sense, the aim of all true sacrifices is to obtain a positional advantage. However, there are some speculative sacrifices where the compensation is in the form of an open file or diagonal or a weakness in the opponent's pawn structure, and it is not even clear how this might potentially be turned into something more tangible. These are the hardest sacrifices to make; they require deep strategic understanding.

Bishops Sacrifice. This involves sacrificing a bishop in the beginning of the game to get an extra pawn and not allow the opponent to castle.

Pseudo sacrifices

Checkmate. A common benefit of making a sacrifice is to allow the sacrificing player to checkmate the opponent. Since checkmate is the ultimate goal of chess, the loss of material (see chess piece point value) should not matter in a successful checkmate. Sacrifices leading to checkmate are typically forcing, and often checks, leaving the opponent with only one or a few options (example, checking the king with the knight, queen takes the knight, then rook checkmates the king with absence on the queen).

Avoiding loss. The counterpart to the above is saving a lost game. A sacrifice could be made to force stalemate or perpetual check, to create a fortress, or otherwise force a draw, or to avoid even greater loss of material.

Material gain. A sacrifice might initiate a combination that results in an overall material gain, making the upfront investment of the sacrifice worthwhile. A sacrifice leading to a pawn promotion is a special case of this type of sacrifice.

Simplification. Even if the sacrifice leads to net material loss for the foreseeable future, the sacrificing player may benefit because they are already ahead in material and the exchanges simplify the position making it easier to win. A player ahead in material may decide that it is worthwhile to get rid of one of the last effective pieces the opponent has.

Other types of sacrifices

Forced vs. non-forced

Another way to classify sacrifices is to distinguish between forcing and non-forcing sacrifices. The former type leave the opponent with no option but acceptance, typically because not doing so would leave them behind in material with no compensation. Non-forcing sacrifices, on the other hand, give the opponent a choice. A common error is to not recognize when a particular sacrifice can be safely declined with no ill-effects.

Miscellaneous sacrifices

A tactical sacrifice can be categorized further by how the sacrifice works, although some sacrifices may fall into more than one category.
In deflection sacrifices the aim is to distract one of the opponents pieces from a square where it is performing a particular duty.
In destruction sacrifices a piece is sacrificed in order to knock away a materially inferior, but tactically more crucial piece, so that the sacrificing player can gain control over the squares the taken chessman controlled.
A magnet sacrifice is similar to a deflection sacrifice, but the motivation behind a magnet sacrifice is to pull an opponent's piece to a tactically poor square, rather than pulling it away from a crucial square.
In a clearance sacrifice the sacrificing player aims to vacate the square the sacrificed piece stood on, either to open up for his own pieces, or to put another, more useful piece on the same square.
In a tempo sacrifice, the sacrificing player abstains from spending time to prevent the opponent from winning material because the time saved can be used for something even more beneficial, for example pursuing an attack on the king or guiding a passed pawn towards promotion.
In a suicide sacrifice, the sacrificing player aims to rid himself of the remaining pieces capable of performing legal moves, and thereby obtain a stalemate and a draw from a poor position.

Examples

A deflection sacrifice

In the diagram , GM Aronian's queen on d3 is at the top of the ladder, and his rook on d1 represents the bottom. He mistakenly played 24. exd4??, opening up the e-file for black's rook. After Svidler played 24. ...Re1+!, Aronian was forced to resign, because Black's move forces the reply Rxe1 (or Qf1 Rxf1+ Rxf1 which amounts to the same thing), after which White's queen is undefended and therefore lost.

This particular type of sacrifice has also been called the "Hook and Ladder trick", for the White queen is precariously at the top of the "ladder", while the rook is at the bottom, supporting it.

A sacrifice to avoid losing

Black played 1...Qxg3? and White drew with 2. Qg8+! Kxg8 (on any other move black will get mated) 3. Rxg7+!. White intends to keep checking on the seventh rank, and if Black ever captures the rook it is stalemate.

This save from Evans has been dubbed "The Swindle of the Century". White's rook is known as a desperado.

A non-forcing sacrifice

This time Reshevsky is at the receiving end of a sacrifice. White has just played h2-h4. If Black takes the knight he will soon get mated on the h-file, but he simply ignored the bait and continued developing.

A positional sacrifice

Black played 1... d4! 2. Nxd4 Nd5. In exchange for the sacrificed pawn, Black has obtained a semi-open file, a diagonal, an outpost on d5 and saddled White with a backward pawn on d3. However, it is by no means clear that this is adequate compensation. The game was eventually drawn.

References

Andrew Soltis. The Art of Defense in Chess. McKay Chess Library, 1975. ISBN 0-679-14108-1.
Leonid Shamkovich. The Modern Chess Sacrifice. Tartan Books, 1978. ISBN 0-679-14103-0.
Israel Gelfer. Positional Chess Handbook. B. T. Batsford Ltd., 1991. ISBN 0-7134-6395-3.
Evans - Reshevsky, USA 1963 (java interface)