50-move rule

The 50-move rule in chess states that a game is considered a draw if one of the two players proves that neither a stone was captured nor a pawn was drawn in the last 50 consecutive moves by either player . After 75 such moves, the game must be counted as a draw by the referee according to the 75-move rule .

Exact definition

In the rules of the World Chess Federation FIDE , draw is defined as follows by the 50-move rule under 9.3:

"9.3 The game is drawn on the basis of a correct request by the player whose turn it is, if

• 9.3.1 he writes a move that cannot be changed on his score sheet and declares to the referee his intention to make this move, which will result in the last 50 consecutive moves of each player being made without that a pawn has moved and without a piece being captured, or
• 9.3.2 the last 50 consecutive moves have been completed by each player without a pawn having moved and without a piece being captured. "

The 75 move rule is defined under 9.6.2:

"9.6 If either or both of the following situations occur, the game is drawn:

• 9.6.1 as soon as the same position has arisen at least five times in accordance with Article 9.2.2,
• 9.6.2 as soon as at least 75 moves have been made by each player without a pawn having moved and without a piece having been captured. If the last move mates, this has priority. "

Practical meaning

The 50-move rule is intended to prevent endless moving back and forth on the chessboard without permanent changes to the position pattern. A chess position can only be changed irreversibly if

• a farmer prefers
• a stone is struck,
• if a rook or the king is moved from the original square for the first time, the future right to one or both castling is lost
• or after a pawn has made a double move, a capture en passant is possible but not taken.

The game is not automatically drawn after 50 moves, but the draw must be claimed by a player. According to the FIDE chess rules , this can only be done by the player whose turn it is. This is one of the reasons for the notation requirement for tournament games. It is entirely possible that a game will continue beyond the point at which a draw can be claimed for the first time. Theoretically, a game could go on indefinitely according to the rules, but in practice at least one of the two players will usually be interested in claiming a draw. Since 2014, according to FIDE rules, the game has to be declared a draw by the referee after 75 moves in the sense of the 50-move rule in order not to disrupt the timing of a tournament.

The roots of the 50-move rule go back to the 16th century. A text by Ruy López de Segura on chess from 1561 already contains details about it. The number of 50 moves was originally determined because in the endgame, runner, knight, king against king in the most unfavorable starting position with perfect play on both sides, 33 moves are required before mate.

In the 1980s, with the help of endgame databases, it was discovered that some endgames can only be won with more than 50 moves or only from certain positions. Examples are pair of bishops and king against knight and king or also certain positions in which rook and bishop fight against a rook . FIDE added exceptions to the rule in December 1984, which allowed 100 moves for certain material distributions, especially in the rook and bishop against rook endgame. After protests by many grandmasters , FIDE initially reduced this number to 75. All these exceptions were canceled on January 1, 1993, and since then all material combinations have been subject to the 50-move rule again.

Rarely are games ended before the endgame due to the 50-move rule. One example is the game Filipowicz – Smederevac from 1966, which ended after move 70 without capturing a single piece - the last pawn was moved on move 20. In 2005, a game between Pouw and Van Dort ended after move 69 with the 50-move rule. It was beaten in it, but after move 19 there were neither blow nor pawn moves.

Chess math

There are extensive studies - first carried out in 1911 by T. R. Dawson  - of the maximum number of moves a game of chess can consist of if the players cooperate in constructing the longest possible game, but every player claims a draw according to the 50-move rule as soon as possible . There are 5899 trains.

There are a maximum of 30 strokes and a maximum of 6 × 16 = 96 pawn moves in a game of chess . So that the white and black pawns facing each other in pairs on each of the eight lines can "get past" each other, either the white or the black pawn of each pair must make a capture move. Thus a maximum of 30 + 96 - 8 = 118 periods are possible without a pawn or capture move.

If the player who made the last pawn or stroke move before such a period also makes the next pawn or stroke move, then a maximum of 99 half-moves without a pawn or stroke can be made in between. If, on the other hand, black and white alternate to make a stroke or pawn move next, then only a maximum of 98 half-moves can be made in between without a pawn and stroke move. At least three such changes are necessary:

	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

An example game after move 249: Black previously played 50.… c7xNd6, 100.… b7 – b6, 150.… f7xNe6 and 200.… g7 – g6. Now White begins with 250. a2 – a3 to move the pawns forward and to convert, for which the a, b, d, e, g and h pawns each have to capture a black piece.

Black begins. He captures one or both white knights and positions the pawns appropriately (first change, see diagram), then White makes seven or six more pawn moves and converts the pawns (second change), then Black captures the remaining white pieces with the exception of the white king and converts the pawns (third change), then white captures the remaining black pieces with the exception of the black king.

Thus the number of half-moves is at most (118 - 3) × 100 + 3 × 99 = 11,797 = 2 × 5898 + 1. Therefore the game must end with the 5899th move by White.

In practice, such long games do not occur. The game between Thomas Ristoja and Jan-Michael Nykopp 1971 (Open Championship of Finland), in which they agreed on a draw after 300 moves and almost 15 hours of play, is well known.

Niels Høeg
Chess Amateur , 1926

	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

See text

A game in which the 50-move rule was in effect from the start and in which chess was never bid ends with the position Kh1, Ka8 after the maximum number of possible moves. Which was the last move?

Solution:
5899. Kg2xRh1
A black knight or bishop would not be enough because of a dead position . A queen would offer chess, but that was ruled out. The king must have come from g2 for the same reason. The number of moves results from the calculations for the longest game.

literature

• Eero Bonsdorff, Karl Fabel , Olavi Riihimaa: Chess and Numbers . Entertaining chess math. 3rd, unchanged edition. Rau, Düsseldorf 1978, ISBN 3-7919-0118-4 (first edition 1966).

Individual evidence

1. ↑ FIDE Laws of Chess taking effect from January 1, 2018 FIDE . Retrieved August 26, 2020.
2. ↑ ^{a b} Translation of the FIDE Laws of Chess: The FIDE - Chess Rules of the German Chess Federation . Retrieved August 26, 2020.
3. ^ A user quotes Stewart Reuben. Geurt Gijssen : New Rules Redux . chesscafe.com. January 2014 .: "The main concern is not to prolong games on a tight schedule."
4. ↑ Bonsdorff et al. a .: chess and tails. Entertaining chess math. Pp. 11-13.