The zwischenzug, also known as an intermezzo or in-between move, is a strategic maneuver in chess where a player deviates from the expected move, typically a recapture, by first making a different move that immediately threatens the opponent. Only after the opponent responds to the threat does the player make the intended move. This tactic grants the player a higher level of initiative. The zwischenzug aims to alter the game’s dynamics in favor of the player, either by gaining material or by avoiding a strong continuation that the opponent would otherwise have. In cases where the intermediate move involves a check, it may be referred to as an in-between check, zwischenschach, or zwischen-check.
In fact, the intermezzo concept became an integral part of certain openings as well. A good example is the Intermezzo Variation (it’s even in the name) of the Scotch Game:
(You can find the rest of the game analysis in the original article (TODO: article link).)
A nice zwischenzug can be found in one of the famous games of Paul Morphy:
Zwischenzugs can occur at any stage of the game, from the opening to the endgame, and can be executed by both sides. It is a valuable technique to have in one’s arsenal as it adds depth and unpredictability to one’s gameplay, often catching opponents off guard and leading to advantageous positions.