- Zugzwang, which is:
In chess, zugzwang (German for "compulsion to move") occurs when one player is put at a disadvantage because he or she has to make a move — the player would like to pass and make no move, but the fact that the player must make one means being forced into a weaker position. Normally in chess, having tempo is a good thing, since the player with the chance to move has greater power by being able to choose the "best" next move. Zugzwang typically occurs when all the moves available are "bad" moves, and better moves might be available if the player did not need to move at the current moment. Zugzwang most often occurs in the endgame when the number of pieces, and so the number of possible moves, is reduced, and the exact move chosen is often more critical. For instance an endgame: wKd5, bPe5, wPe4, bKf4. Whoever is to move in this position loses the game — they must abandon their own pawn, thus allowing their opponent to capture it and go on to promote their own pawn. Because this is zugzwang no matter who is to move next, this is an example of:

- mutual or reciprocal zugzwang.

So we have 2 terms of which second is only a part of first. The second term (mutual or reciprocal zugzwang), which is subterm of zugzwang obviously makes confusion in chess world.

The point of having a tempo in chess is improvement of our position, because we have a power to make the choice to improve the position with the very next move. In a rare case when having a tempo can only worsen our position (no matter which legal move we make) - exactly then we can speak about zugzwang. If our opponent moves again and we can only worsen the position again, then we can say we had two zugzwangs in a row and so on.

The point is that by triangulation (to refer only to one of techniques in e.g. K+Ps endings) and other techniques of "catching the right time to be on the right spot" you can make favor of the situation the way its your opponent who has to move when it comes down to mutual zugzwang.

I will give you a simple example of mutual zugzwang with only 1 pawn left: White-Kb6, Pc7, Black-Kc8. With these 3 pieces only on the board, whoever turn it is, he loses instantly (or in case of white's move he only manages to draw). As said - with the right technique you can make mutual zugzwang work for you if you make sure its your opponent who has to move first.

In addition to the case above, had white additional pawn on - let's say - c4, then its not Mutual zugzwang anymore but it is a "unmutual" = normal = basic zugzwang, because white has an option of moving c4-c5, which is not a draw yet.

<Sneaky> already explained it here Kaplan vs Bronstein, 1975

You can find the theory about zugzwang and mutual zugzwang here:

http://www.calchess.org/information...

page 24 - mutual zugzwang (case)

Of course it is important. The knowledge (as in the link of a case i submitted) is the difference not only between winning and drawing but usually even losing (e.g. technique, how to approach to the couple of pawns in a trebuchet position - who gets there second, wins). Maybe it doesn't occur very often in play, but it sure is most important to know when it comes down to it.

click for larger view

Whoever has the move loses. It is called a trébuchet. But I agree with the comments of <paladin at large>