In chess, a sacrifice is a move giving up a piece with the objective 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 may be sacrificed. Because players usually try to hold on to their own pieces, offering a sacrifice can come as an unpleasant surprise to one's opponent, putting him off balance and causing much precious time to be wasted 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.
Types of sacrifice
Real versus sham
proposed a division between sham and real sacrifices:
In a real sacrifice, the sacrificing player will often have to play on with less than his opponent for quite some time.
In a sham sacrifice, the player offering the sacrifice will soon regain material of the same or greater value, or else force mate. A sham sacrifice of this latter type is sometimes known as a pseudo sacrifice.
In compensation for a real sacrifice, the player receives dynamic, positional, or other non-material advantages which he must capitalize on, or risk losing the game due to the material deficit. Because of the risk involved, real sacrifices are also called speculative sacrifices.
Real sacrifices
;Attack on the king ;Development ;Strategic/positional
Sham sacrifices
;Checkmate ;Avoiding loss ;Material gain ;Simplification The tactical sham sacrifices can be categorized further by the mechanism in why the sacrifice is made. Some sacrifices may fall into more than one category.
In deflection sacrifices, the aim is to distract one of the opponent's 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 lines 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.
Other types of sacrifices
Forced versus 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.
Examples
Deflection sacrifice
In the diagram, GM Aronian has 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 25. Rxe1, 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.
Suicide sacrifice
Black played 1... Qxg3? and White drew with 2. Qg8+! Kxg83. Rxg7+!. White intends to keep checking on the seventh, 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.
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 has to give up his own knight on f6 to avoid mate on h7. Instead, he simply ignored the bait and continued developing.
Positional sacrifice
In this game Black played 14... d4! 15. 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. The game was eventually drawn.
In this position, Black moves 22... Qg1+ forcing the white rook to take black's queen by 23. Rxg1 ; the king cannot take the queen because it would have been in check from the knight on h3. Having forced the rook out of a position where it was defending the f-file and into a position where it blocked the king from making any move, the black knight delivers a smothered mate by 23... Nf2#.
