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Subject: Re: King Night Bishop - 50 Moves

Author: Marc Plum

Date: 22:18:56 04/22/99

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On April 22, 1999 at 13:05:04, Steve Coladonato wrote:

>At one time, there was a rule in chess that in the case of a known forced mate a
>player was allowed the standard 50 move rule or twice the number of moves with
>best play to execute the mate.  The KNB vs K ending is a 34 move ending  with
>best play.  Therefore a player was allowed 68 moves to effect the mate.  Does
>anyone know if this rule is still in effect?

The idea was never to give extra time to force the win, if it could be done in
less than 50 moves.  The limit was extended in certain positions where the win
could be forced only if the players were allowed to make more than 50 moves
without a pawn advance or a capture.

I'm looking at the obsolete 1984 edition of the FIDE rules (given in the 1987
edition of USCF's *Official Rules of Chess*).  Article 10.9 of the FIDE rules
extended the 50 move rule to 100 moves in the following cases.

1 KBR against KR

2 K and 2 Knights against K and P with following conditions. Pawn is safely
blocked by a knight, and pawn is now further advanced (for Black) than a4, b6,
c5, d4, e4, f5, g6, or h4.  If White has the pawn, and Black has the Knights
then use the corresponding squares for the White Pawns.

3 KRP vs KBP if
a: White has the Rook, a pawn at a2, Black has a pawn at a3 and a Black squared
Bishop.
b: White has the Rook, a pawn at h2, Black has a pawn at h3 and a White squared
Bishop.
c: Same positions with colors reversed (e.g. Black has the Rook, Black pawn at
a7, etc.

This rule no longer exists AFAIK.  The latest edition of the FIDE rules that I
have is from 1992, and article 10.9 does not even deal with the same point.
Article 10.12 still provides for the theoretical possibility that the limit
might be extended for certain positions, however, but does not give any
examples.  Most people probably did not bother to learn the theory of these
endings; I certainly never did.

Marc



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