The zwischenzug (German: pronounced ˈtsvɪʃənˌtsuːk "intermediate 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 (Hooper & Whyld 1992:460) (Golombek 1977:354). 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 (Cox 2007:216), intermediate move (Kasparov 2008:208), or in-between move (Burgess 1997:494) (Horowitz & Reinfeld 1954:180–97). When the intermediate move is a check, it is sometimes called an "in-between check" (Horowitz & Reinfeld 1954:183–85), "zwischenschach" (van Perlo 2006:479), or "zwischen-check" (Mednis 1997:270).

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.

Wikipedia article: Zwischenzug