Three-check chess

What this variant is

Three-check is standard chess plus one winning condition. The starting array, the piece moves, castling, capture in passing and promotion are all unchanged. What is added is a running count of the checks each player has given, and a third check ends the game.

The counter

• Each side has its own counter, starting at zero, and the two are kept separately. Your checks never cancel your opponent’s.
• A move that leaves the enemy king in check adds one to your counter, however it happens: an ordinary attack, a discovered attack, a check delivered by a promoted piece, or a check given while castling.
• A move counts once. If it attacks the king with two men at the same time, that double check still adds one.
• Reaching three ends the game immediately in favour of the player who gave the third check. Nothing else needs to happen.

Being in check is answered exactly as usual: move the king, capture the attacker, or block the line. There is no way to decline a check, and no way to bring a counter back down once it has gone up. Both counters are shown to both players throughout the game, so neither side is ever guessing how close the end is.

Winning

• Giving your third check. The game ends at once.
• Checkmate, exactly as in standard chess, and it still ends the game immediately even if your counter is only at one.
• Resignation, or the opponent running out of time.

Drawing

The ordinary draws all apply: stalemate, agreement, threefold repetition, the fifty-move rule, a dead position, and a timeout against an opponent with no mating material. Repetition and the fifty-move rule are applied automatically for both sides.

Repetition is worth thinking about here. A player one check from losing may want to shuffle, and a player one check from winning almost never does, so drawn positions are rarer than in the standard game. A perpetual check, which draws in standard chess, is simply a win here.

How it changes your play

• Spending a pawn or even a piece to open a line at the enemy king is often a good trade. A pawn is worth a pawn; a check is worth a third of the game.
• Castling is not automatically safe. A castled king on g1 can be checked along the a7-g1 diagonal and down the h-file, and both are easy to open.
• Blocking a check with a piece is usually better than moving the king, because a king that has moved often becomes easier to check again.
• Count before you calculate. If the opponent has two checks, every forcing line you allow has to be checked for a third.