In chess

Chess

Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...

, decoying is the tactic

Chess tactic

In chess, a tactic refers to a sequence of moves which limits the opponent's options and may result in tangible gain. Tactics are usually contrasted with strategy, in which advantages take longer to be realized, and the opponent is less constrained in responding.The fundamental building blocks of...

 of ensnaring a piece, usually the king or queen, by forcing it to move to a poisoned square with a sacrifice

Sacrifice (chess)

In chess, a sacrifice is a move giving up a piece 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....

 on that square.

The diagram on the right, with Black to play, illustrates two separate decoys. First, the White queen is set up on c4 for a knight fork: 1... Rxc4! 2. Qxc4. Next, the fork is executed by removing the sole defender of the a3 square: 2... Qxb2!+ 3. Rxb2 Na3+ 4. Kc1. Finally, a zwischenzug

Zwischenzug

The zwischenzug is a chess tactic in which a player, instead of playing the expected move first interpolates another move, posing an immediate threat that the opponent must answer, then plays the expected move...

 decoys the king to b2: 4... Bxb2+. After either 5. Kxb2 Nxc4+ 6. Kc3 Rxe4, or 5. Kd1 Nxc4, Black is two pawns ahead and should win comfortably.

Perhaps the most celebrated game featuring a decoy theme is Petrosian

Tigran Petrosian

Tigran Vartanovich Petrosian was a Soviet-Armenian grandmaster, and World Chess Champion from 1963 to 1969. He was nicknamed "Iron Tigran" due to his playing style because of his almost impenetrable defence, which emphasised safety above all else...

 - Pachman

Ludek Pachman

Luděk Pachman was a Czechoslovak-German chess grandmaster, chess writer, and political activist. In 1972, after being imprisoned and tortured almost to death by the Communist regime in Czechoslovakia, he was allowed to emigrate to West Germany...

, Bled 1961 (java interface), which also involved a queen sacrifice.