Looking at the Batsford pawn endings book, which looks at critical positions, one can easily see that W pawns on g5 and h5 and B long on h8 is the critical position since g6 wins from this position. It doesn't matter how you get to the critical position. This is easier than memorizing a one time rule.









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TopNotch wrote on 08/15/21 at 17:18:55:

I was only trying to answer the question "I would like to know whether this rule is limited only to "Rook & Knight Pawn vs Rook Pawn" or does it apply to all Pawn Endings?", thus my terseness. Thanks for providing the additional info.

an ordinary chessplayer wrote on 08/15/21 at 19:49:54:

I presume that Bird is Henry Bird, the same player that Bird's Opening (1.f4) is named after, and that he was the first person to formulate the rule. But that's just guessing.

Vishnu wrote on 08/14/21 at 14:15:37:


He didn't really clarify it at all so allow me.



In the above diagram Bird's Color Rule goes like this: When the Kings are on opposite color squares White's pawns also need to be on opposite colored and conversely when the Kings are on the same colored squares then White's pawns need to be on the same squares as each other. 

For example in the diagrammed position the Kings are on opposite colored squares so we place our pawns on opposite colored squares 1.g4 when Black goes 1...Kh8 the Kings are on same color squares so we place our pawns on the same squares as each other with 2.h3 and we eventually win using this method while had we mindlessly played 2.h4?? we would have allowed Black to draw.

As pointed out by Dfan, Bird's Color Rule is a useful calculation shortcut in a specific position that could also have been easily solved by counting, in essence White must be able to push g6 when the Black King is on h8 forcing him to give up the Opposition. Opposition and Triangulation being the most important rules in pawn endings, master those and you can usually work out the rest with a little brain power.

You're welcome.   

Postscript: Just wanted to mention before someone else does, that the most important take away from the diagrammed position is that it doesn't really matter in what order White's pawn reaches g5 so long as we are able to follow up with either h3 or h4 depending on Black's king position.

Bird's rule applies only to a very specific position where White (say) has an advanced king, g-pawn, and h-pawn, and Black has an h7 pawn with a king behind it (or the same position on the queenside of course). It's just a calculation shortcut because you need the kings to be in a particular state when your pawns have finished advancing. There is no relevance to any other pawn ending.

There's a similar kind of rule when Black has a king on h1, a pawn on h2, and a knight, and White is deciding whether to put their king on f1 or f2.