zugzwang

Compulsory move is a situation in games with alternating compulsory moves, in which the party having the move would have an advantage if not they but the other party had to make a move. A game with alternating moves is chess , for example . In most games there is hardly any compulsion to move, as a player can usually make a move that at least does not worsen his situation. In chess, however, many finals can only be won by the opposing forces.

In colloquial terms, the term “ Zugzwang”, on the other hand, usually describes a situation in which someone is forced to take a certain action or, in general, to react to a challenge. This action can, but does not necessarily have to, have adverse consequences.

To the subject

The German chess player Max Lange is named as the originator of the technical term . The earliest known use was in an article in the Berliner Schachzeitung in 1858 . The word was adopted as Germanism in many languages, including English and Russian . The Oxford English Dictionary cites a reference from Lasker's Chess Magazine (February 1905, p. 166) published by the then world chess champion Emanuel Lasker .

A crime novel by the Northern Irish author Ronan Bennett , set against the backdrop of the 1914 chess tournament in Saint Petersburg , was published in 2006 under the title Zugzwang .

Mutual pressure to act

A situation in which each of the two players (if it was their turn) is forced to move is called a mutual forced move (sometimes also reciprocal or mutual forced).

	a	b	c	d	e	f	G	H
8th									8th
7th									7th
6th									6th
5									5
4th									4th
3									3
2									2
1									1
	a	b	c	d	e	f	G	H

Mutual pressure to act

White has an extra pawn and wants to win the game, Black wants to save himself in a draw . In the diagram position, however, there is mutual pressure:

• If it is White's turn, he can only achieve a draw: If his king moves to c6, Black is patted . On all other king moves, the black king captures the then unprotected white pawn on c7, after which the game is also drawn.
• If it is Black's turn, he loses: Because 1.… Kc8 – b7 is the only possible and therefore forced move. This is followed by the second Kd6-d7 and the next train of white pawn reaches the eighth row with conversion into a lady or a tower, after which White in a few trains matt sets.

The following example shows a mutual pressure to move in which the player whose turn it is loses. The train obligation costs not only half a point, but even a whole point.

	a	b	c	d	e	f	G	H
8th									8th
7th									7th
6th									6th
5									5
4th									4th
3									3
2									2
1									1
	a	b	c	d	e	f	G	H

Mutual pressure to act

In the position in the diagram, both players are again forced to act.

Both kings have attacked the opposing pawn and defend their own pawn at the same time. In your turn you have to give up the protection of your own pawn, you lose this and with it the game.

This motif is known as a trebuchet (especially in the English-speaking world) .

The link at the end of the article may show a. the application of the Trébuchet motif in a complex pawn ending.

Importance in chess composition

In chess composition , Zugzwang is often used as a paradoxical element . For example, special programs were used to systematically search the endgame databases for positions of mutual forced access and these positions were published in the EG magazine .

Train change maneuvers

In order to put the opponent in a tight spot, move change maneuvers are carried out, especially in the endgame :

• The simplest case is a waiting train . This is a move that does not create any new threats, but maintains all the essential possibilities of its own position.
• If there is no waiting move, a so-called triangle maneuver is often used.
• However, there are also other train change maneuvers. Manfred Zucker’s assignment , Der Tagesspiegel, September 30, 1990 shows how the lady describes a trapeze in order to set a tempo.

Establishing a forced tension position

Alekhine - Nimzowitsch
San Remo , 1930

	a	b	c	d	e	f	G	H
8th									8th
7th									7th
6th									6th
5									5
4th									4th
3									3
2									2
1									1
	a	b	c	d	e	f	G	H

Position after 31.… g7 – g6
White to move wins

Black had already given up after 30. h4. After the possible sequence of moves 30.… h5 31. Kh2 g6 the position in the diagram emerges. If White now moves 32. g2 – g3 , Black is forced to move: The knight on c6 is pinned and the other pieces are tied to the defense of this knight, the king has to defend c7. G6 – g5 is simply followed by Nf3xg5. As soon as Black then has to move a piece, his position collapses: After a move by the knight e7 follows Bxc6, other moves are answered with b5 plus a piece win.

Further practical examples of a Zugzwang are the Immortal Zugzwang game and the game Bogoljubow - Alekhine, Hastings 1922 .

Problems in chess programming

	a	b	c	d	e	f	G	H
8th									8th
7th									7th
6th									6th
5									5
4th									4th
3									3
2									2
1									1
	a	b	c	d	e	f	G	H

Diagram 1 : Difficult problem for a chess computer!

	a	b	c	d	e	f	G	H
8th									8th
7th									7th
6th									6th
5									5
4th									4th
3									3
2									2
1									1
	a	b	c	d	e	f	G	H

Diagram 2 : Black sacrifices the rook in order to achieve this profitable forced move.

In chess programming, forced move positions are a problem for widespread pruning algorithms such as the Nullmove algorithm, since its premise is no longer fulfilled in a forced move position.

In the diagram position (1) it is not uncommon for a computer to only recognize a draw. Black's way of winning consists of 1.… Rd6 – d7 + 2. Kg7 – g8 (or f8, g6 or h6 with move change ) 2.… Rd7 – d8 + 3. Kg8 – g7 . Thereupon Black positions his rook uncovered on h8 with 3.… Rd8 – h8. If White decides to capture the rook with 4. Kg7xh8 , Black can lock up White's king with 4.… Ke6 – f7 and thus reach the position in diagram (2).

White is forced to move with the pawn on b2 or h2, as his king cannot move on h8. If White moves with the h2-pawn, the black king swings between the squares f7 and f8, so that the white king remains locked up. As soon as the h2-pawn has reached h6, he cannot move either. White is forced to move and must move b2 – b4 or b2 – b3. Then beats black with a4xb3 (possibly in passing ) the white b-pawn and sets white with following b3-b2-B1D ( conversion in lady) and D b1-a1 Matt or b3-b2-B1T ( conversion tower) and TB1 b8 matt. A possible variant is: 5. 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 11. a4-a5 b2-b1D 12. a5-a6 Qb1-a1 #.

If White does not capture black rook after 3.… Rd8 – h8, the black king swings between e7 and e8, or if White moves Kh6, between f6 and f7, until White runs out of pawn moves again. Then White must capture the rook on h8, whereupon the black king moves to f7 (with transition to the variant described above), or moves Kg7 – g6, whereupon Black wins with Ke7 – f8.

Further examples of forced entry

• Henry Augustus Lovedays Dreizüger, see Indian problem

literature

• Alex Agnos: You move, I win . Thinker's Press, Davenport 2005, ISBN 1-888710-18-7 .

Individual evidence

1. ↑ Golombek : The Penguin Encyclopedia of chess , as well as various websites (search query: Trebuchet + chess)

Web links

Wiktionary: Zugzwang  - explanations of meanings, word origins, synonyms, translations

• http://chess.jaet.org/cgi-bin/mzüge List of all mutual forced draft positions with up to 6 stones (English)
• http://www.herderschach.de/Training/Online/index-tr001.html#a1a Simple and complex examples of the Trébuchet for online replay