Bughouse chess is a popular chess variant played on two chessboards by four players in teams of two. It is also known as exchange chess, tandem chess, transfer chess, double bughouse, doubles chess, cross chess, swap chess, or simply bughouse, bugsy, or bug.Other less common names for bughouse include Team chess, Hungarian chess, Swedish chess, New England Double bughouse, Pass-On chess, Tandem Put-Back, Double Speed, Double chess, Double Five, Simultaneous chess, Double bug or Double bughouse (von Zimmerman (2006), front; Manson and Hoover (1992), p. 186 and "Bughouse and Tandem Chess" The Chess Variant Pages). See Bughouse in other languages . Accessed July 29, 2007. The name Siamese chess is also used but should not be confused with Thai chess. Normal chess rules apply, except that captured pieces on one board are passed on to the teammate on the other board, who then has the option of putting these pieces on their board.
The game is usually played at a fast time control. Together with the passing and dropping of pieces, this can make the game look chaotic to the casual onlooker, hence the name bughouse, which is slang for mental hospital.Bughouse. Merriam Webster website. Accessed December 2, 2020. Yearly, several dedicated bughouse tournaments are organized on a national and an international level.__TOC__
Rules
Bughouse is a chess variant played on two boards by four players in teams of two. Each team member faces one opponent of the other team. Partners sit next to each other and one player per team has black pieces, while the other has white pieces. Each player plays the opponent as in a standard chess game, with the exception of the rules specified below.Bughouse has many variations and there is no international standard. The rules below are in accordance with the US chess federation, the rules as applied on the chess servers Free Internet Chess Server and Internet Chess Club and the Berlin bughouse tournament. In the case rules contradict, alternatives are listed. Accessed July 29, 2007.
Captured pieces A player capturing a piece immediately passes that piece to their partner. The partner keeps these pieces in their reserve and may, on their turn, instead of playing a regular move, place one of these pieces on the board (as in shogi, crazyhouse or Hostage Chess), called dropping the piece. Pieces in reserve may be dropped on any vacant square, including squares where the piece delivers check or checkmate; however, pawns may not be dropped on the first or last . (A variant does not allow dropped pieces to deliver check.Reglement Doorgeefschaak ("Passing chess rules") , retrieved February 7, 2022.) Dropped pawns may promote, but all promoted pawns convert back to pawns when captured. In play over the board, a promoted pawn can be put on its side to indicate promotion.von Zimmerman (2006), p. 15 A pawn placed on the second rank (its typical starting square) may move two squares on its first move, and, if it lands directly next to an enemy pawn, be captured en passant. A rook placed on its typical starting square (a1, h1, a8, h8) may take part in castling. Each player must keep the reserve or stock pieces on the table in front of the board, always visible to all players of the game.
Clock and completion of a move Bughouse chess is usually played with chess clocks to prevent players from waiting indefinitely to be passed a piece. Clocks are placed on the outside of the adjacent boards so that all players can see both clocks. At the start of the game, the players with the black pieces start the clocks simultaneously. Bughouse is usually played using , meaning players are committed to a move only after pressing the clock. is practiced to a lesser extent.See for example the rules of the Geneva bughouse tournament. Accessed July 29, 2007. When used, it applies to pieces in reserve as well; they are considered dropped after contact has been made with an empty square.
Bughouse can be played without a clock, but then there is usually a rule preventing a player waiting for pieces (stalling or sitting) indefinitely. One rule states that players may not delay their move beyond the time that it takes for their partner to make three moves.
End of the game The match ends when the game on either board ends. A game is won when one player gets checkmated, resigns, runs out of time, or makes an illegal move. The match can be drawn by agreement or when two players on opposite teams run out of time or are checkmated simultaneously. Threefold repetition may apply to a single board; however, players should be mindful that if the reserve of pieces is taken into account (e.g., even if one board repeats the same position after three moves), it is not a draw if the piece reserve changes. Internet Chess Club considers the reserve pieces in evaluating threefold repetition, but both FICS and chess.com rule a draw by threefold repetition on the board without considering the reserve pieces.
Alternatively, when one board finishes, play can continue on the other board. In this case, pieces in reserve can still be dropped, but no new pieces are coming in. If the players who won their games were on opposite teams, the outcome of the match is then decided by adding the score of the two boards, or the victorious players may play against each other.
Communication Partners are normally allowed to talk to each other during the game. They can, for instance, ask for a specific piece, for more trades, ask to hold a piece, suggest moves or ask their partner to stall. Shouts like "Knight mates!" or "Don't give up a Bishop!" are common and can lead to seemingly absurd sacrificial captures on the other board. Partners are not allowed to physically act on the other board.See Article nr. 12, US Chess Federation bughouse rules. Accessed August 27, 2007.
Two-player and six-player variations It is possible to play the game with just two players by having each player move on two boards. Analogously to simultaneous chess, this way of playing the game is referred to as simultaneous bughouse. It can also be played with just one clock by playing the boards in a specific order (White A, White B, Black B, Black A) and pressing the clock after each move. This variation is suitable for correspondence play.von Zimmerman (2006), p. 108
Bughouse can be played with three or more boards. The game is played in exactly the same way as normal bughouse with boards placed with alternating colours and two players and one clock per board. On capturing a piece however, the player may have to decide which player of the team will get that piece. In three-board bughouse chess, the middle player is the key since they get material from two boards, but have to decide how to divide the captured pieces.Manson and Hoover (1992), pp. 34–37 The middle board also commonly becomes very cramped due to having twice the number of extra pieces available.
Strategy
Material In chess, a minor material advantage is important as when material gets exchanged, the relative advantage becomes larger. Because new pieces come in, there is no endgame play in bughouse and material is therefore less important. It is common to sacrifice pieces in bughouse while attacking, defending, or hunting down a certain piece which one's partner requires.
The material balance of a position can be calculated by adding up the piece values of each player's pieces. In standard chess, a pawn equals one unit, a bishop or knight is worth three, a rook five and a queen nine. These values are a consequence of the difference in mobility of the pieces. Bughouse piece values differ because pieces in reserve essentially have the same mobility as they can be dropped on any vacant square.von Zimmerman (2006), p. 17 The pawn relatively gains importance in bughouse chess, as its very limited mobility does not handicap reserve pawns. They can, for instance, be dropped to block non-contact checks. Pawns can be dropped onto the seventh rank, one step away from promotion, which further adds to their importance. Long-range pieces like the queen or the rook lose relative value, due to the constantly changing pawn structure. They are also more likely to be hemmed in.Manson and Hoover (1992), pp. 32–33 A valuation system, first suggested by the popular and one-time highest rated bughouse player André Nilsson of Sweden ("Gnejs" on ICC, FICS, and chess.com), often applied to bughouse is pawn=1, bishop=knight=rook=2 and queen=4.von Zimmerman (2006), p. 17. The bughouse playing program Sunsetter uses the values pawn=100, bishop=195, knight=192, rook=200 and queen=390, while the engine Sjeng uses pawn=100, bishop=230, knight=210, rook=250 and queen=450. Accessed July 29, 2007.
Coordination Captured pieces are passed on, and thus what happens on one board influences what happens on the other board. It is, therefore, natural for team members to communicate during game play. A common request of an attacking player would be "trades are good," while players in trouble may ask their partners to hold trades with "trades are bad." Similarly, a player can request a piece (e.g. "knight wins a queen") or ask their partner to hold a piece (e.g. "rook mates me").von Zimmerman (2006), pp. 243–44
Another common situation in the interplay between the two boards is a player not moving, a strategy known as sitting or stalling. Stalling can happen in anticipation of a certain piece or at the request of the partner. If, for example, a player is under heavy attack, and an additional pawn would mate them, but their partner cannot prevent giving up a pawn on the next move, sitting is the only strategy. It would, however, be perfectly logical for the attacker to sit as well, waiting for a pawn to come. The situation where diagonal opponents sit at the same time is known as a "sitzkrieg" (literally "sitting war" in German, and a pun on "blitzkrieg"). The difference in time between the diagonal opponents will eventually force one party to move. This diagonal time advantage is more important than the difference on the clock between opponents on the same board.Manson and Hoover (1992), pp. 75–89 At the higher levels (>2000), players move very quickly, especially in the opening, as a time advantage of as little as 10 seconds can be more important than seemingly decisive positional advantages.Chuck Moulton, annotating a Bughouse World Championship match, January 30, 2022. Retrieved February 1, 2022.
Apart from active communication, a good bughouse player tries to coordinate silently by keeping an eye on the other board and adapting moves accordingly. This can mean as little as glancing at the other board before trading queens, or as much as playing an opening adapted to the other board.See Chris Ferrante (2000) , reproduced in von Zimmerman (2006), pp. 79–94
Attack and defense Attacking the king can mean checking the opponent but also controlling vital squares around the king. It is an essential part of bughouse gameplay. From a player's perspective, attacking the king has important advantages as opposed to defending or attempting to win material:von Zimmerman (2006), p. 109 Because of the possibility of dropping pieces, attacks in bughouse can quickly lead to checkmate. The attacking player has the initiative; the attacker controls the board, while their opponent is left to react. This fact has important consequences for the other board as well. It is easier to attack than to defend. A defensive mistake can have bigger consequences than an offensive mistake. Thus, the defender needs to be more precise, which, in turn, can lead to a time advantage for the attacker.