This article uses algebraic notation to describe chess moves.

Zugzwang (German for "compulsion to move", pronounced [ˈtsuːktsvaŋ]) is a term originally used in chess which also applies to various other games. The concept finds its formal definition in combinatorial game theory. It describes a situation where one player is put at a disadvantage because he has to make a move – the player would prefer to pass and make no move. The fact that the player must make a move means that his position will be significantly weaker than the hypothetical one in which it is his opponent's turn to move.

In game theory, it specifically means that it directly changes the outcome of the game from a win to a loss. The term is used less precisely in games such as chess; e.g., the game theory definition is not necessarily used in chess (Berlekamp, Conway & Guy 1982:16), (Elkies 1996:136). For instance, it may be defined loosely as "a player to move cannot do anything without making an important concession" (van Perlo 2006:479). Zugzwang is a common technique to help the superior side win a game and sometimes it is necessary to make the win possible (Müller & Pajeken 2008:173).

The term zugzwang is frequently used in chess. A player whose turn it is to move who has no move that does not worsen his position is said to be in zugzwang (Soltis 2003a:78). Thus every move would make his position worse, and he would be better off if he could pass and not move. Sometimes different chess authors use the term zugzwang in different ways (Flear 2004:11-12). In some literature a reciprocal zugzwang (see below) is called zugzwang and a one-sided zugzwang is called a squeeze (Hooper & Whyld 1992).

The term zugzwang was used in German-language chess literature in 1858 (or earlier) (Winter 1997). The first known use of the term in English was by World Champion Emanuel Lasker in 1905 (Winter 2008). The concept of zugzwang (as distinguished from the word) must have been known to players many centuries earlier, since it is necessary to win the elementary king and rook versus king endgame, among others. The concept is also seen in an endgame study published in 1604 by Alessandro Salvio, one of the first writers on the game. It also appeared in Shatranj studies dating back to the early 9th century, over 1000 years before the first known use of the term zugzwang.

In a chess endgame, being in zugzwang usually means going from a drawn position to a loss or a won position to a draw, but it can be from a win to a loss, or a substantial loss of material which probably affects the outcome of the game. A chess position of reciprocal zugzwang or mutual zugzwang is equivalent to the more precise definition of zugzwang in game theory. Opposition is a special kind of zugzwang (Flear 2000:36). Trébuchet is a special type of zugzwang that is discussed below.

Positions with zugzwang occur fairly often in chess endgames. For instance, twelve of the 105 endgames in the book Endgame Virtuoso Anatoly Karpov involve zugzwang (Karolyi & Aplin 2007:358). National Master Alex Angos wrote an entire book about zugzwang, You Move ... I Win! (Angos 2005). According to John Nunn, positions of reciprocal zugzwang (see below) are surprisingly important in the analysis of endgames (Nunn 1995:6), (Nunn 1999:7).

The remainder of this article is about zugzwang in chess.

Contents 1 Introduction 2 History 3 Examples from games 3.1 Fischer versus Taimanov, 1971, second match game 3.2 Fischer versus Taimanov, 1971, fourth match game 3.3 Tseshkovsky versus Flear, 1988 4 Reciprocal zugzwang 4.1 Second example 4.2 Examples from play 4.3 Trébuchet 4.3.1 Examples 4.3.2 Example in study 4.3.3 Analysis from actual game 4.3.4 In endgame study 5 Mined squares 6 Zugzwang required to win 7 Zugzwang helps the defense 7.1 In a study 8 Zugzwang in the middlegame and complex endgames 8.1 Sämisch versus Nimzowitsch 8.2 Steinitz versus Lasker 8.3 Podgaets versus Dvoretsky 8.4 Harper versus Zuk 8.5 Van Dongen versus Wijsman 8.6 Zhilin versus Chernov 8.7 Fischer versus Rossetto 8.8 Example from Euwe and Meiden 9 Zugzwang Lite 10 Quotation 11 See also 12 Notes 13 References 14 Further reading 15 External links

[edit] Introduction

There are three types of chess positions:

1. both sides would benefit if it were their turn to move
2. only one player would be at a disadvantage if it were his turn to move
3. both players would be at a disadvantage if it were their turn to move.

The great majority of positions are of the first type. In chess literature, most writers call positions of the second type zugzwang, and the third type reciprocal zugzwang or mutual zugzwang. Some writers call the second type a squeeze and the third type zugzwang (Hooper & Whyld 1992) (Hooper 1970:196-97).

Normally in chess, having tempo is desirable because the player who is to move has the advantage of being able to choose a move that improves his situation. Zugzwang typically occurs when all the moves available are "bad" moves, tangibly weakening the moving player's position (usually from a draw to a loss or from a win to a draw) (Müller & Lamprecht 2001:22).

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 critical. The diagram at top right shows the simplest possible example of zugzwang. If it is White's move, he must either stalemate Black with 1.Kc6 or abandon the pawn, allowing 1...Kxc7 with a draw. If it is Black's move, the only legal move is 1...Kb7, which allows White to win with 2.Kd7 followed by queening the pawn on the next move.

The diagram at below right is another simple example. Black, on move, must allow White to play Kc5 or Ke5, when White wins one or more pawns and can advance his own pawn toward promotion). White, on move, must retreat his king, when Black is out of danger (Flear 2004:11-12). The squares d4 and d6 are corresponding squares. Whenever the white king is on d4 with White to move, the black king must be on d6 to prevent the advance of the white king.

In many cases, the player having the move can put the other player in zugzwang by using triangulation; that article has an illustrative example. Zugzwang is very common in king and pawn endgames, where it is frequently achieved through triangulation. Pieces other than the king can also triangulate to achieve zugzwang – e.g., see the queen versus rook position at Philidor position. Zugzwang is a mainstay of chess compositions and occurs frequently in endgame studies.

Andy Soltis notes that many players do not appreciate zugzwang, thinking that it is an obscure concept that never occurs in their games. Without zugzwang, it would be very hard to win a chess game, even with an extra piece (Soltis 2009:15).

[edit] History

According to chess historian Edward Winter (Winter 1997), in German, the term "zugzwang":

had been in regular use in the nineteenth century. Pages 353-358 of the September 1858 Deutsche Schachzeitung had an unsigned article 'Zugzwang, Zugwahl und Privilegien'. F. Amelung employed the terms Zugzwang, Tempozwang and Tempozugzwang on pages 257-259 of the September 1896 issue of the same magazine. When a perceived example of Zugzwang occurred in the third game of the 1896-97 world championship match between Steinitz and Lasker, after 34...Rg8, the Deutsche Schachzeitung (December 1896, page 368) reported that 'White has died of Zugzwang'.

The earliest known use of the term "zugzwang" in English was on page 166 of the February 1905 issue of Lasker's Chess Magazine (Winter 2008). The term did not become common in English-language chess sources until the 1930s, after the publication of the English translation of Nimzowitsch's My System in 1929 (Winter 1997).

The concept of zugzwang, if not the term, must have been known to players for many centuries. Zugzwang is required to win the elementary (and common) king and rook versus king endgame (Soltis 2003a:79), and the king and rook (or differently-named pieces with the same powers) have been chess pieces since the earliest versions of the game (Davidson 1981:21-22,41).

The earliest use of zugzwang (other than in basic checkmates) may be in this study by Zairab Katai, which was published sometime between 813 and 833. (This study was actually from the predecessor of chess Shatranj but the moves of the king, rook, and knight are the same. Masters of this era composed many studies in which Black was in zugzwang so that any move fatally weakened his position.) After

1. Re3! Ng1

2. Kf5! Kd4

3. Kf4

puts Black in zugzwang, since 3... Kc4 4. Kg3! Kd4 5. Re1 and White wins (Soltis 2009:15).

The concept of zugzwang is also seen in the 1585 endgame study by Polerio at right, published in 1604 by Alessandro Salvio, one of the earliest writers on the game. Angos (2005:108-9) gives the position as by Giulio Cesare Polerio in 1585. The only way for White to win is 1.Ra1!! Kxa1 2.Kc2!, placing Black in zugzwang. His only legal move is 2...g5, whereupon White promotes a pawn first and then checkmates with 3.hxg5 h4 4.g6 h3 5.g7 h2 6.g8(Q) h1(Q) 7.Qg7# (Sukhin 2007:21,23).

Joseph Bertin in The Noble Game of Chess (1735), which Hooper and Whyld consider "the first worthwhile chess textbook in the English language", referred to the concept of zugzwang, albeit without using that word, when he set forth as the 18th of his 19 rules about chess play, "To play well the latter end of a game, you must calculate who has the move, on which the game always depends." (Hooper & Whyld 1992:38-39).

François-André Danican Philidor wrote in 1777 of the position at below right that after White plays 36.Kc3, Black "is obliged to move his rook from his king, which gives you an opportunity of taking his rook by a double check, or making him mate" (Philidor 2005:272-73).^{[note 1]} Lasker explicitly cited a mirror image of this position (White: king on f3, queen on h4; Black: king on g1, rook on g2) as an example of zugzwang in Lasker's Manual of Chess (Lasker 1960:37-38). The British master George Walker analyzed a similar position in the same endgame, giving a maneuver that resulted in the superior side reaching the initial position, but now with the inferior side on move and in zugzwang. Walker wrote of the superior side's decisive move: "throwing the move upon Black, in the initial position, and thereby winning" (Walker 1846:245).

The great American player Paul Morphy (1837–1884), like Salvio and Philidor an unofficial World Champion, is credited with composing the position at right "while still a young boy". After 1.Ra6!, Black is in zugzwang and must allow mate on the next move with 1...bxa6 2.b7# or 1...B (moves) 2.Rxa7# (Shibut 2004:297).

[edit] Examples from games

[edit] Fischer versus Taimanov, 1971, second match game

Some zugzwang positions occurred in the second game of the 1971 candidates match between Bobby Fischer and Mark Taimanov.^[1] In the position in the diagram, Black is in zugzwang because he would rather not move, but he must: a king move would lose the knight, while a knight move would allow the passed pawn to advance (Wade & O'Connell 1972:413). The game continued:

85... Nf3

86. h6 Ng5

87. Kg6

and Black is again in zugzwang. The game ended shortly (because the pawn will slip through and promote) (Kasparov 2004:385):

87... Nf3

88. h7 Ne5+

89. Kf6 1-0.

[edit] Fischer versus Taimanov, 1971, fourth match game

In the position on the right, White has just gotten his king to a6, where it attacks the black pawn on b6, tying down the black king to defending it. White now needs to get his bishop to f7 or e8 to attack the pawn on g6. Play continued:

57... Nc8

58. Bd5 Ne7

59. Bc4! Nc6

60. Bf7 Ne7

Now the bishop is able to make a tempo move. It is able to move while still attacking the pawn on g6, and preventing the black king from moving to c6.

61. Be8

and Black is in zugzwang. Knights are unable to make a tempo move (Nunn 1995:7), so moving the knight would allow the bishop to capture the kingside pawns. The black king must give way.

61... Kd8

62. Bxg6! Nxg6

63. Kxb6 Kd7

64. Kxc5

and White has a won position. Either one of White's queenside pawns will promote or the white king will attack and win the black kingside pawns and a kingside pawn will promote. Black resigned seven moves later (Silman 2007:516-17), (Averbakh 1984:113-14), (Flear 2007:286-87). Andy Soltis says that this is "perhaps Fischer's most famous endgame" (Soltis 2003b:246).

[edit] Tseshkovsky versus Flear, 1988

This position from a 1988 game between Vitaly Tseshkovsky and Glenn Flear shows an instance of "zugzwang" where the obligation to move makes the defense more difficult but it does not mean the loss of the game. A draw by agreement was reached eleven moves later (Flear 2007:241).^[2]

[edit] Reciprocal zugzwang

A special case of zugzwang is reciprocal zugzwang or mutual zugzwang, which is a position such that who ever is to move is in zugzwang. Positions of reciprocal zugzwang are surprisingly important in the analysis of endgames (Nunn 1995:6), (Nunn 1999:7). A position of mutual zugzwang is closely related to a game with a Conway value of zero in game theory (Stiller 1996:175).

The diagram on the right shows a position of reciprocal zugzwang. If Black is to move, he must move 1... Kd7 and lose because White will move 2. Kb7, promote the pawn, and win. If White is to move, he must either move 1. Kc6 which is a draw because it stalemates Black or he must abandon the pawn, which is also a draw after Black captures the pawn. Both sides would be in zugzwang if it were their move, so it is a reciprocal zugzwang (Hooper 1970:21), (Averbakh 1993:35).

In a position with reciprocal zugzwang, only the player to move is actually in zugzwang. However, the player who is not in zugzwang must play carefully because one inaccurate move can cause him to be put in zugzwang (Müller & Pajeken 2008:179). That is in contrast to regular zugzwang, because the superior side usually has a waiting move to put the opponent in zugzwang (Nunn 1999:7).

[edit] Second example

Another example is shown in the diagram on the right – if White is to move the game is drawn; if Black is to move he loses. With White to move:

1. Kd5 Kd7

2. c5 Kc7

3. c6 Kc8!

4. Kd6 Kd8!

Black has the opposition and draws because 5. c7+ Kc8 6. Kc6 is stalemate.

If Black is to move, White wins

1. ... Kd7

2. Kb6 Kc8

3. Kc6 Kd8

and White wins with

4. Kb7

or

4. c5 (Flear 2004:22), (see king and pawn versus king endgame).

[edit] Examples from play

The position at right is a position that could have occurred in the 1961 game between Viacheslav Kalashnikov and the young Anatoly Karpov. White to move in this position draws, but Black to move loses. Karpov's 49th move in the actual game avoided the zugzwang and the game was drawn (Karolyi & Aplin 2007:22). This is one of 209 mutual zugzwang positions in the rook and pawn versus rook endgame (Nunn 1999:7).

The second position is an analysis position from the ninth game of the 1984 World Chess Championship between Anatoly Karpov and Garry Kasparov. The alternate move 45... Ke6 is considered and this position could result after move 57. White to move draws; Black to move loses. It would have been White's move in this analysis position. Kasparov played a different 45th move and Karpov won after seventy moves (Kasparov 2008:111), (Karolyi & Aplin 2007:269).

[edit] Trébuchet

An extreme type of reciprocal zugzwang, called trébuchet is shown in the third diagram. It is also called a full-point mutual zugzwang because a full point (win versus loss) is at stake. Whoever is to move in this position loses the game—they must abandon their own pawn, thus allowing their opponent to capture it and proceed to promote their own pawn (Flear 2004:13).

[edit] Examples

This diagram shows a position in which a trébuchet can be reached to win the game. The first king to reach the blocked pawns will win. Play continues:

1. Kxh6 Kxc3

2. Kg5 Kd3!

2... Kd4?? loses because after 3. Kf5 Black is on the wrong side of the trébuchet.

3. Kf5 Kd4!

and Black wins the pawn and the game (see King and pawn versus king endgame) (Silman 2007:98).

Another simple example is seen in the diagram at right. Black, on move, must play 1...b3, allowing 2.axb3#. White, on move, must move his king away, allowing 1...b3, with an easy win for Black.

[edit] Example in study

This position is a mutual zugzwang from a 1792 study. The first player to move runs out of moves and loses (Speelman 1981:43).

[edit] Analysis from actual game

In this analysis from a 1978 game between Miguel Najdorf and Henrique Mecking, whoever is to move loses. (It would have been White's move had the analysis position occurred in the game.) (Silman 2007:385-87)

[edit] In endgame study

Marc Bourzutschky has used computer analysis to find some complicated trébuchet positions. If White is to move in this position, Black quickly drives White's king toward the corner and mates no later than move 8, e.g. 1.Kb2 (1.Nhg7 Qf4+ or 1.Nh4 Qe3+ also leaves White's king in trouble) Qg2+ 2.Kb3 Qb7+! 3.Ka3 Qb6 4.Nf4+ Kc4! 5.Ka2 Qb3+! 6.Ka1 Kb4 7.Ng7 Ka3 8.Nge6 Qb2#. Black on move must give ground, enabling White to gradually improve the positions of his pieces, e.g. 1...Kc4 (1...Kc3 allows 2.Nf2! Qxf2?? 3.Ne4+) 2.Kd2! Kd5 3.Ne3+ Ke5 4.Ng7 and White mates by move 42 according to Bourzutschky.-- scroll down to No. 282

[edit] Mined squares

Mined squares are squares such that a player will fall into zugzwang if he moves onto the square. In the diagram on the right, if either king moves onto the square marked with the dot of the same color, he falls into zugzwang if the other king moves into the mined square near him. These are a type of corresponding squares (Dvoretsky 2006:19).

[edit] Zugzwang required to win

In some endgames it is necessary to place the opponent in zugzwang in order to force a win. These include:

• rook (and king) versus king checkmate
• two bishops versus king checkmate
• two knights versus pawn checkmate
• Bishop and knight checkmate
• queen versus rook
• queen versus knight
• queen versus two knights, and
• queen versus two bishops (Soltis 2003a:79).

In addition, zugzwang is required in many king and pawn versus king endgames in order to force promotion of the pawn and in other king and pawn endgames with more pawns (Müller & Pajeken 2008:173). (See pawnless chess endgame and fortress (chess) for some discussion of some of these endings.)

[edit] Zugzwang helps the defense

Zugzwang usually works in favor of the stronger side, but sometimes it aids the defense. In this position based on a game between Zoltán Varga and Peter Acs, it saves the game for the defense:

1... Kc4!! Reciprocal zugzwang

2. Nc3 Kb4 Reciprocal zugzwang again

3. Kd3 Bg7 Reciprocal zugzwang again

4. Kc2 Bh6

5. Kd3 Bg7

6. Nd5+ Kxa4

7. Ke4 Kb5

8. Kf5 Kc5

9. Kg6 Bd4

10. Nf4 Kd6

11. h6 Ke7

12. h7 Bb2

This position is a draw and the players agreed to a draw a few moves later (Müller & Pajeken 2008:179-80).

In this position from Benko, White should win but he makes an error and gets into zugzwang which enables Black to draw.

1. Kd6? Bb7

2. Bd7 Bf3

3. Be6 Bb7!

and Black draws because White is in Zugzwang (Fine & Benko 2003:153-54).

[edit] In a study

This position is a 1901 endgame study by Amelung. White to move wins by taking the opposition after 1. Kb7! and putting Black in zugzwang, e.g. 1... Kc4 2. Kb6 b3 3. Ka5 Kc3 4. Ka4 b2 5. Ka3 and White wins the pawn. In 1956 Ilyia Maizelis pointed out that Black to move can take the opposition and put White in zugzwang:

1... Kc5!

2. Kb7 Kb5!

3. Ka7 Ka5!

and White cannot make progress (Angos 2005:109-10).

[edit] Zugzwang in the middlegame and complex endgames

Alex Angos notes that, "As the number of pieces on the board increases, the probability for zugzwang to occur decreases." (Angos 2005:178) As such, zugzwang is very rarely seen in the middlegame (Angos 2005:183).

[edit] Sämisch versus Nimzowitsch

The game Fritz Sämisch versus Aron Nimzowitsch, Copenhagen 1923,^[3] is often called the "Immortal Zugzwang Game".^{[note 2]} Some consider the final position to be an extremely rare instance of zugzwang occurring in the middlegame (Reinfeld 1958:90). It ended with White resigning in the position in the diagram.

White has a few pawn moves which do not lose material, but eventually he will have to move one of his pieces. If he plays 1.Rc1 or Rd1, then 1...Re2 traps White's queen; 1.Kh2 fails to 1...R5f3, also trapping the queen, since White cannot play 2.Bxf3 because the bishop is pinned to the king; 1.g4 runs into 1...R5f3 2.Bxf3? Rh2 mate. Angos analyzes 1.a3 a5 2.axb4 axb4 3.h4 Kh8 (waiting) 4.b3 Kg8 and White has run out of waiting moves and must lose material. Best in this line is 5.Nc3!? bxc3 6.bxc3, which just leaves Black with a serious positional advantage and an extra pawn (Angos 2005:180). Other moves lose material in more obvious ways.

However, since Black would win even without the zugzwang (Nunn 1981:86), it is debatable whether the position is true zugzwang. Even if White could pass his move he would still lose, albeit more slowly, after 1...R5f3 2.Bxf3 Rxf3, trapping the queen and thus winning queen and bishop for two rooks (Horowitz 1971:182). Wolfgang Heidenfeld thus considers it a misnomer to call this a true zugzwang position (Golombek 1977). See also Immortal Zugzwang Game: Objections to the sobriquet.

[edit] Steinitz versus Lasker

This game between Wilhelm Steinitz versus Emanuel Lasker in the 1896-97 World Chess Championship,^[4] is an early example of zugzwang in the middlegame. After Lasker's 34...Re8-g8!, Steinitz resigned because he has no playable moves.^{[note 3]} White's bishop cannot move because that would allow the crushing ...Rg2+. The queen cannot move without abandoning either its defense of the bishop on g5 or of the g2 square, where it is preventing ...Qg2#. White's move 35.f6 loses the bishop: 35...Rxg5 36. f7 Rg2+, forcing mate. The move 35.Kg1 allows 35...Qh1+ 36.Kf2 Qg2+ followed by capturing the bishop. The rook cannot leave the first rank, as that would allow 35...Qh1#. Rook moves along the first rank other than 35.Rg1 allow 35...Qxf5, when 36.Bxh4 is impossible because of 36...Rg2+; for example, 35.Rd1 Qxf5 36.d5 Bd7, winning. That leaves only 35.Rg1, when Black wins with 35...Rxg5! 36.Qxg5 (36.Rxg5? Qh1#) Qd6+ 37.Rg3 hxg3+ 38.Qxg3 Be8 39.h4 Qxg3+ 40.Kxg3 b5! 41.axb5 a4! and Black queens first (Reinfeld & Fine 1965:71). Colin Crouch calls the final position, "An even more perfect middlegame zugzwang than ... Sämisch-Nimzowitsch ... in the final position Black has no direct threats, and no clear plan to improve the already excellent positioning of his pieces, and yet any move by White loses instantly" (Crouch 2000:36-37).

[edit] Podgaets versus Dvoretsky

Soltis writes that his "candidate for the ideal zugzwang game" is the following game (Soltis 1978:55) : Podgaets-Dvoretsky, USSR 1974 1.d4 c5 2.d5 e5 3.e4 d6 4.Nc3 Be7 5.Nf3 Bg4 6.h3 Bxf3 7.Qxf3 Bg5! 8.Bb5+ Kf8! Black exchanges off his bad bishop, but does not allow White to do the same. 9.Bxg5 Qxg5 10.h4 Qe7 11.Be2 h5 12.a4 g6 13.g3 Kg7 14.0-0 Nh6 15.Nd1 Nd7 16.Ne3 Rhf8 17.a5 f5 18.exf5 e4! 19.Qg2 Nxf5 20.Nxf5+ Rxf5 21.a6 b6 22.g4? hxg4 23.Bxg4 Rf4 24.Rae1 Ne5! 25.Rxe4 Rxe4 26.Qxe4 Qxh4 27.Bf3 Rf8!! 28. Bh1 28.Qxh4? Nxf3+ and 29...Nxh4 leaves Black a piece ahead. Ng4 29.Qg2 (see diagram at left) Rf3!! 30.c4 Kh6!! (diagram at right) Now all of White's piece moves allow checkmate or ...Rxf2 with a crushing attack (e.g. 31.Qxf3 Qh2#; 31.Rb1 Rxf2 32.Qxg4 Qh2#). That leaves only moves of White's b-pawn, which Black can ignore, e.g. 31.b3 Kg7 32.b4 Kh6 33.bxc5 bxc5 and White has run out of moves.^{[note 4]} 0-1

[edit] Harper versus Zuk

Harper-Zuk, Halloween Open, Burnaby, British Columbia 1971^[5] is a grisly example of zugzwang in the middlegame. White's queen, rook, knight, and king have a total of one legal move (Qh3), which loses the queen and king on successive moves (... gxh3 followed by ... Qxg2#). The game concluded: 37.b5 Kh8 37...Nf5 and Nd4-e2 was crushing, but letting White self-destruct is even quicker. 38.a4 Kh7 39.a5 Kg8 0-1 After 40.axb6 axb6, white is forced to play 41.Qh3, and then it is mate in two: gxh3 42.Kh2 Qxg2#.

[edit] Van Dongen versus Wijsman

An unusual example of zugzwang in a complicated endgame occurred in the position at right. On the previous move Black, with a winning position, had played 73...d4? and White responded 74.Rd2-d3!!, when Black, a knight up with three dangerous passed pawns, suddenly must fight for a draw. Tim Krabbé explains that the pawns on d4 and e4 are blocked and pinned, the knight is bound to the defense of e4, the rook is bound to the defense of d4, and the pawn on b4 is bound to the defense of the knight. Krabbé analyzes as best for Black 74...b3! 75.Rxd4 Rxd4 76.Rxc3 Rd8 77.Rxb3 Re8 78.Re3 Re5 79.Rc3 (79.Kxf6? Rxa5 82.Kg6 Ra1 83.f6 Rg1+ wins) Re8 80.Re3 Re5 81.Rc3 and the game will end in a draw by repetition of moves. Instead, Black played 74...Nb5? 75.Rxe4 Nd6 76.Re6 Rc6 77.Rxd4 Rxh6+ 78.Kxh6 Nxf5+ 79.Kg6 1-0 ^[6].

[edit] Zhilin versus Chernov

In the game between Vitaly Valentinovich Zhilin and Chernov (or Tchernov), White was a pawn down and just sacrificed a bishop on h3. After 1. Kh4! Black is placed in zugzwang after moving his b- and h-pawns. The game continued:

1. Kh4! b6

2. Kh5 b5

3. Kh4 h5

4. Kxh5

Now Black is in zugzwang and resigned (Nunn 1981:86-87), (van Perlo 2006:71).

[edit] Fischer versus Rossetto