Tandem Chess

Tandem Chess

Tandem Chess (also known as Siamese Chess) is a 4-player team chess variant played on two simultaneous standard boards. It is closely related to Bughouse Chess and shares most of its rules, with two key distinctions. It is one of the most widely played team chess formats internationally.

Setup

Two standard 8×8 boards:

• Board A: White1 (Team A) vs Black1 (Team B)
• Board B: White2 (Team A) vs Black2 (Team B)

Teams: White1 + White2 vs Black1 + Black2. Partners sit on the same side of the table. On each board, one team member plays White and the other plays Black.

The Relay Mechanic

When a player captures an enemy piece, it is passed to their partner on the other board. The partner may drop (place) the received piece onto any empty square on their board in lieu of making a normal move.

Drop restrictions:

• A Pawn may not be dropped on the 1st or 8th rank.
• A piece may not be dropped on an occupied square.
• Special rule: A player may not give check or checkmate by dropping a piece (this is the key Tandem Chess restriction that distinguishes it from Bughouse).

Additional drop rules:

• A Rook dropped on either of its home squares (a1/h1 for White, a8/h8 for Black) is treated as unmoved and may be used for castling.
• A Pawn dropped on the 2nd rank inherits the two-step advance option and is subject to en passant capture.

Win Condition

The match continues until both boards have been completed (not just the first checkmate). After both games end, the score is counted:

• 1 point for a win on a board
• ½ point for a draw
• 0 points for a loss

The team with the higher total score wins. If teams score 1–1, the match is a draw.

Turn Order

Play proceeds as in standard chess on each board — White1 and Black1 alternate on Board A; White2 and Black2 alternate on Board B. Partners may not advise each other, but may request a specific piece type (e.g., “Partner, I need a Knight”).

Key Differences from Bughouse Chess

Tandem Chess differs from Bughouse in two rules:

1. No check or checkmate by drop — dropped pieces may not place the enemy King in check.
2. Both games must complete — the match is not decided by the first checkmate; both boards are played to completion.

Attribution

Rules documented from chessvariants.com/multiplayer.dir/tandem.html (Hans Bodlaender, 1996; edited John William Brown).