The zwischenzug (German: pronounced [ˈtsvɪʃənˌtsuːk], "intermediate move"; also called an in-between move) is a chess tactic in which a player, instead of playing the expected move (commonly a recapture), first interposes another move posing an immediate threat that the opponent must answer, and only then plays the expected move.[1][2] It is a move that has a high degree of "initiative". Ideally, the zwischenzug changes the situation to the player's advantage, such as by gaining material or avoiding what would otherwise be a strong continuation for the opponent.
Such a move is also called an intermezzo[3] (lit. 'intermediate move')[4] or in-between move.[5][6] When the intermediate move is a check, it is sometimes called an in-between check,[7] zwischenschach,[8] or zwischen-check.[9]
As with any fairly common chess tactic, it is impossible to pinpoint when the first zwischenzug was played. Three early examples are Lichtenhein–Morphy, New York 1857; Rosenthal–De Vere, Paris 1867; and Tartakower–José Raúl Capablanca, New York 1924. The first known use of the term zwischenzug, however, did not occur until 1933, when the prolific American chess authors Fred Reinfeld and Irving Chernev used it in their book Chess Strategy and Tactics.