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This page is written by the game's inventor, Ralph Betza.

Lag Chess

Lag Chess is a moderated game of incomplete information in which you must reply to your opponent's most recent move without knowing what it was.


Each move must be sent, not to the opponent, but to a moderator.

The moderator has the duty of deciding whether or not the move is legal. If it is not legal, the player must make a different move.

Each turn, the moderator sends the previous move, but not the most recent move, to the player whose turn it is.


The moderator must validate this move, send the accepted this move to the player who made the move and send this player's last move to the opponent. The rule can be confusing until you get used to it.

Are There Any?

This is not Kriegspiel. In Lag Chess you have much more information than in Kriegspiel. You must try the possible Pawn captures.

You should send to the moderator a list of moves; the first move on the list that is legal will be accepted. This is a time-saving measure, and is not required by the rules; however, this time-saver is what makes Lag Chess possibly more attractive than Kriegspiel for play by mail.

Your opponent does not get to hear how many pawn captures you attempted. This is not Kriegspiel.


1. e4 d5 2. (e4-f5 rejected, e4-d5 accepted), (Qd8-d5 accepted) 3. (d5-c6 rejected, d5-e6 rejected, d5-d6 rejected, Nb1-c3 accepted) 3... (Qd5-h1 rejected, Qd5-a5 accepted)

4. (Ra1-a2 rejected, Bf1-g2 rejected, Bc1-d2 rejected, g2-f3 rejected, a2-b3 rejected, c2-d3 rejected)

When White plays this move, it is known that the Q was on d5; therefore, the precautionary moves guarding against random capture are necessary.

Notice that after 3...Qxa2?, White does not know that a2 was captured.

After the rejections, White knows that the Black Queen is either on d5, d4, e5, e4, e6, d6, d7, d8, c6, c5, c4, b5, a5, g5, f5, or h5. In many of these cases, the Q is hanging, if White just knew where. Therefore, the move to try is 4. Bf1-b5 accepted.

On Black's 5th move, what to do? b4xa5 might be threatened. If Qa5-b4 is tried and accepted, the response might be a3xb4. Probably 3. Qd5-a5 was a bad move.

Try 5...Qa5-h5 rejected. Now Black knows the move was either Nd5 or Nb5 or Bb5. Try 5...Qa5-d5 rejected, try 5...Ng8-f6 rejected, try c7-c6 accepted, and then on Black's 6th move,

Should we try 5..c6xb5? Bad idea, the response might be b4xa5. Safest is 5...Qa5-d8!


I am not a good Kriegspiel player. Lag Chess appears to me to be playable, but one cannot be certain unless some experienced Kriegspiel players try it.

Lag Chess is certain to be more fun than editing this file in vi with a fifteen-second lag. (It just now happened, but only once...)

Different Armies

Lag Chess with Different Armies works perfectly well.


It might be possible to play not knowing your opponent's last two moves. To me, that seems utterly confusing, but players who like games of incomplete information, and who have become skilled at them, might actually find "Lag 2 Chess" preferable.

Notice that in Doublemove Lag Chess, you don't know your opponent's last turn, which contains two moves. In Doublemove Lag 2 Chess you don't know two turns, which equals four moves.

"Lag Infinity Chess" is Kriegspiel, but with a slight difference. When you play Kriegspiel live, with three people in the same location, asking "are there any?" is actually more convenient than trying all the likely Pawn captures as is done in Lag Chess. However, in Kriegspiel one is supposed to be able to gain information by hearing how many Pawn captures and how many illegal moves were tried.

In Progressive Avalanche Chess, there is only one unknown. Part of your opponent's move was to advance one of your Pawns, and this part of the move must be made known to you. Often you can infer something about the unknown move from the Pawn push.

Written by Ralph Betza.
WWW page created: April 10, 2003.