Marseillais chess

In Marseillais chess, a player makes two consecutive moves before yielding the turn. The same piece may move twice, or two different pieces may move once each. This modest rule changes calculation dramatically: a piece can approach and capture within one turn, or a threat can be prepared and executed without an intervening reply.

A widely used balanced form gives White only one move on the first turn. Black then makes two moves, White makes two, and play continues in double-move turns. Without that initial adjustment, moving first and immediately receiving a full two-move sequence would give White an especially large advantage.

How check works

Check means that the king is under attack. The check rules prevent players from treating the two moves as permission to leave the king temporarily exposed. If a player begins a turn in check, the first move must remove it. A king also cannot enter an attacked square on the first move and escape on the second.

If the first move of a turn gives check to the opposing king, the turn ends and the second move is forfeited. Giving check too early can therefore be less forceful than it first appears: it compels a reply but also gives up the chance to complete another action.

Strategic consequences

• Two-step threats are immediate. One piece can open a line and another can exploit it during the same turn.
• An attacked piece can escape and use the second move to create a threat of its own.
• King safety requires anticipating complete two-move sequences rather than one isolated reply.
• Move order matters. Two moves that are legal separately may form an illegal sequence if the first leaves the moving side's king in check.

The allowance remains fixed at two moves, unlike progressive chess, where the number rises from turn to turn. Published rule sets also differ on some special cases, so players should agree on a specific version before starting.

The variant appeared in 1925 in the Marseille newspaper Le Soleil. Its identity comes not from a new starting array or extra pieces, but from the basic unit of play: each player must think in connected pairs of moves.