Zugzwang

Zugzwang is a situation in games with alternating Zugpflicht, in which each turn of the on- train party has an adverse effect on them. A game with alternating Zugpflicht for example chess. In most games Zugzwang hardly occurs because a player usually can make a train, at least not worsen his situation. In chess, however, many playoffs can only be gained by opposing tight spot.

Colloquially, the term Zugzwang in contrast, usually a situation in which someone to a certain action or are generally forced to make a response to a challenge. This action may, but need not necessarily have adverse consequences.

The concept

The author of the medical term, the German chess player Max Lange is mentioned. The earliest known use was in 1858 in an article in the Berliner Zeitung chess. The word has been adopted as Germanism in many languages ​​, including English and Russian. The Oxford English Dictionary cites a passage from the document issued by the former world chess champion Emanuel Lasker Lasker 's Chess Magazine ( February 1905, p 166).

A crime novel of the Northern Irish author Ronan Bennett, who plays in St. Petersburg against the background of the chess tournament in 1914, appeared in 2006 under the title of a tight spot.

Mutual Zugzwang

A situation in which each player is located at the train in a tight spot is called a mutual Zugzwang (sometimes reciprocal zugzwang or mutualer ).

White has an extra pawn and wants to win the game, Black would like to save the draw. In the diagram position, however, is mutual Zugzwang:

• Is White the train, he can only draw achieve: Attracts reign after c6, so Black is stalemate. In all other features of the king black king kicks the then uncovered white pawns on c7, after which the game is also a draw.
• Is Black the train, he loses: For 1 ... KC8 - b7 is the only possible and therefore forced train. This is followed by 2 Kd6 - d7 and the next train, the white pawn reaches the eighth series with transformation into a lady or a tower, after which White plays in a few moves Mate.

The following example shows a mutual Zugzwang, which loses the train located at the player. The Zugpflicht So here costs not just half, but even a whole point.

In the diagram position, are again both players in a tight spot.

This motif is known (especially in the English language ) as Trébuchet.

The listed at end of article link shows, among other things the application of Trébuchet motif in a complex endgame.

Importance in chess composition

In the chess composition Zugzwang is often used as a paradoxical element. So the endgame databases were systematically searched using special programs by mutual positions Zugzwangs and publishes these positions in the Journal of the EC.

Zugwechselmanöver

To put the opponent in a tight spot, Zugwechselmanöver be carried out particularly in the final:

• The simplest case is a waiting move. This is a train that creates no new threats, but maintaining all the essential capabilities of your own position.
• If there is no waiting move, then a so-called triangle maneuver is often used.
• However, there are also other Zugwechselmanöver. The role of Manfred sugar, Der Tagesspiegel, September 30, 1990 shows how the lady describes a trapezoid to post a pace.

Making a Zugzwangstellung

Black had already abandoned after 30.h4. After the possible sequence of moves 30 - h5 31.Kh2 g6 the position in the diagram is created. Attracts White g2 - g3 now 32, Black is in zugzwang: the knight on c6 is tied up and the other characters are tied to the defense of this knight, the king has to defend c7. On g6 - g5 follows simply Sf3xg5. Once Black then has to draw a figure, breaks his position together: After a train of Springer e7 follows Lxc6, other trains are answered with b5 plus figure income.

Other practical examples of a tight spot, the Immortal Zugzwangpartie and the game Bogolyubov - Alekhine, Hastings 1922.

Problems in chess programming

In the chess programming provide Zugzwangstellungen a problem for widespread pruning algorithms such as the zero - Move algorithm because its premise is no longer satisfied in a Zugzwangstellung.

In the diagram position, ( 1) it is not uncommon that a computer does not recognize more than a draw. The second is to a win for Black KG7 - g8 (or f8, g6 or h6 with diverter ) 2 ... TD7 d8 Kg8 - g7 3 in 1 ... Td6 - d7 . Then stationed Black with 3 ... Rd8 - h8 his rook on h8 uncovered. White chooses to be the tower with 4 Kg7xh8 to beat, so Black can with 4 ... Ke6 - f7 the white king imprison and achieve the position in diagram ( 2).

White is forced to draw on b2 or h2, as his king on h8 can not draw with the farmers. Attracts white with the h2 -pawn, the black king commutes between fields f7 and f8, so that the white king remains imprisoned. Once the h2 - pawn has arrived on h6, even this can not draw. White is in zugzwang and must b2- b4 or b2 -b3 draw. Then beats black with a4xb3 (possibly en passant ) the white b -pawn and white sets with the following b3- b2- B1d (convert to Queen) and b1 -a1 -b2 - b3 Matt or B1T (conversion into tower) and Tb1 - b8 matt. One possible approach is: 5th h2 h3 Kf7 -f8 6 h3 - h4 Kf8 - f7 7 h4 - h5 Kf7 -f8 8 h5- h6 Kf8 - f7 9 b2- b4 a4xb3 ep 10 a3 -a4 b3- b2 a4 - a5 b2- 11 B1d 12 a5 a6 - b1 -a1 .

If the black tower white does not strike after 3 ... Rd8 - h8, commutes the black king as long as between e7 and e8, to white again run out of pawn moves. Then White has hit the tower on h8, after which the black king to f7 pulls pull ( with transition in the above-described variant), or KG7 - g6, after which Black wins with Ke7 -f8.

Other examples of a tight spot

• Henry Augustus Love Three Days Züger, see Indian problem