Thursday, 28 March 2013

Bahr's Rule, in King and Pawn endgame


We have been already learnt seven topics in details about king and pawn ending. Now we will go further deep into king and pawn endgame with Bahr's rule.

The rule will quickly help the defender or attacker about winning or drawing a game without calculation in the position where ram on rook file and outsider passer will decide about winning or drawing a game. Ram mean pawn blocked with each other. In simple terminology there are two pawns on rook file which are blocked and stronger side has another outside passed pawn.

Where to apply the rule or preconditions for the Bahr's rule :
Normally it has been seen that in endgame we are lacking in time, in such situation this rule helps a lot in judging the position.

Condition 1  Stronger side 'rook-pawn' has not crossed half of the board. ( Not crossed its 4th rank), if pawn has crossed middle of the board ; stronger side will win other wise we have to use Bahr's rule. 
Diagram # 1
In  diagram#1; we need not to use this rule as pawn has already crossed its half so white can easily win with

1. Kd3 - Kb4
2. Kb4 wins

or 

1. Kd3 - Kc6
2. Kd4- Kd6
3. c5+ - Kc6
4. Kc4 - Kc7
5. Kd5 - Kd7
6. c6+ - Kc7
7. Kc5 - Kc8
8. Kb6, winning another pawn and wins easily with two extra pawns.

Condition 2 Stronger side king stands next to its passed pawn.
Condition 3 Defender king must be standing in front of the passed pawn or the attacking king.


See the below diagram#2, where you have to use Bahr's rule to reduce your calculation in critical time trouble as pawn has not crossed its 4th rank and other conditions are met.
Diagram # 2
Bahr's Border line :
Like in rule of square we need to create square, here in this rule we need to create Bahr's border line.

Step 1 : Draw diagonal from defender pawn to its first rank then stop it in Bishop's file (f or c file)- See the diagram#3
Diagram # 3

Step 2 : Bend the diagonal towards attacker's first rank. See below diagram#4
Diagram # 4

Bahr's rule:
After drawing Bahr's border line in mind, if passed pawn is on or below the border line  ; stronger side wins but if passed pawn is above the border line, the position is drawn. 

So here in diagram#4 if white plays c5+ the game is draw with Kc6 as outside passed pawn is now above the borderline but if white plays Ke4 (aware of rule), he will win with

1. Ke4 - Kc5
2. Kf5 - Kc4
3. Kg5 - Kd5
4. Kxh5 - Ke6
5. Kg6! reaching to the key square and winning the game.

It might be difficult to learn this rule but once you learnt it, you can save lots of time and energy.

5 comments:

  1. Bahr's rule is mentioned in Pump Up Your Rating as one of the things you need to know about pawn endings, but here is the only place i could find and explanation of it. Thanks
    ps not in Comp chess end by averbakh or anywhere else i looked. appreciate it.

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  2. Oops Bahr's rule IS in Averbakh"s pawn ending book, p 78. Very poorly explained your explanation is much better, but it is addressed. Thanks and sorry for the error.

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  3. Thank you for explaining this. I found your lesson very helpful.

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  4. When you bend the line back to the first rank, don't you mean the second rank of the f or c file ie f7 or c7, then forward to the attackers side. It might not intersect if the attacker has a rook pawn or knight pawn, so just draw the second leg and stop when you get to the c2 or f2 point. Now what happens, if the attacker has a passed pawn on the rook or knight file, protected by kings respectively. Can we assume that the attacker only draw at best if not in opposition, wins if has opposition ... the Bahr rule says nothing on this, but what do you think please? thanks

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    Replies
    1. You mean to say ?
      White : h4,b4 and KC4
      Black : a5 Kc6

      if this is the case game is draw as pawn is above the border line... irrespective of opposition.

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