What is Bughouse?
Bughouse is chess for four players in two teams of two, played on two boards at the same time. Partners sit at different boards and play opposite colours: one has White on board A, the other Black on board B. Each board is a fast game of its own, but the two are tied together by captures.
When you capture a piece, it goes to your partner, who keeps it in hand with its colour unchanged and may drop it on any empty square of their board instead of moving. So the queen you win on your board can turn up a moment later next to your partner's opponent's king. Pawns are never dropped on the first or last rank, and a promoted pawn that is captured passes on as a pawn.
Neither board waits for the other: on each board White and Black alternate, and the match ends as soon as one board ends. Checkmate on either board wins for the mating team; running out of time, resigning or leaving loses for that player's team. A player with no move, even in check, is not beaten yet: they wait, clock running, for their partner to send a piece to drop.
Online, four players meet at one table and the computer can fill any empty seat. On one device you play one seat against the computer, which plays your partner and both opponents; there is no passing the device between players.
Rule changes
| Rule | Standard Chess | Bughouse |
|---|---|---|
| Players | Standard ChessTwo players on one board. | BughouseFour players in two teams, on two boards. Board A White and board B Black are one team; board A Black and board B White are the other. |
| Turns | Standard ChessWhite and Black move in turn. | BughouseBoth boards play at the same time. On each board White and Black still move in turn, but nobody waits for the other board. |
| Captured pieces | Standard ChessLeave the game for good. | BughouseGo to your partner's hand, keeping their colour, so your partner can drop them on the other board. A captured promoted pawn goes over as a pawn. |
| Drops | Standard ChessThere are no drops: every turn is a move of a piece on the board. | BughouseInstead of moving, you may place a piece from your hand on any empty square of your board, but a pawn never on the first or last rank. Drops may give check and checkmate. |
| How to win | Standard ChessCheckmate the opponent's king. | BughouseThe first board to finish decides the match. Checkmate on either board wins for the mating team; losing on time, resigning or leaving loses for that player's team. A check that a dropped piece could block is not mate, even when no piece is in hand yet. |
| No legal move | Standard ChessA player with no legal move who is not in check is stalemated, and the game is drawn. | BughouseThere is no stalemate. A player with no move waits, with their clock running, until their partner sends a piece they can drop. |
| Clock | Standard ChessPlayed with or without a clock, as the table chooses. | BughouseAlways timed when played live: a table with no time control chosen gets 3 minutes per player, so nobody can hold up a board while their partner waits. |
| Draws | Standard ChessStalemate, threefold repetition, the fifty-move rule and insufficient material. | BughouseOnly by agreement of all the human players, or by a safety rule: when no player to move on either board can ever move again, or after 800 moves on the two boards together. A message says which rule ended the game. |
History
Little is known about where bughouse began. An American chess encyclopedia of 1956 described a two-player game, under the names bughouse chess and putback chess, in which no piece ever leaves the board: the player who makes a capture puts the captured enemy piece back on an empty square. The chess variant historian David Pritchard dated the four-player team game to the early 1960s, and American newspapers of the early 1970s wrote about it as double bughouse. It has gone by many other names since, among them exchange, tandem, transfer, doubles, swap and Siamese chess.
Bughouse became a popular diversion in local chess clubs in Europe and North America, and it is played as a side event at scholastic championships. It has been played on internet chess servers since the mid-1990s, strong grandmasters have played it in exhibition matches, and online championships are now held every year.
There is no international standard, and clubs and sites differ in details such as whether partners may talk, how repeated positions are counted and whether a check that a drop could block is mate. The rules here follow the common online form: a check that a drop could block is not mate, and a player with no move waits for a piece instead of being stalemated.