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|Elementary endgames (Part 7)|
|An extra Pawn is an advantage; when it's an outside passed Pawn, it's a big advantage.|
Take a look at the diagram below, where White has an extra Pawn on the Queenside. If the Kings were tied down and couldn't move, White would win easily by first advancing the b-Pawn to b5 followed by the a-Pawn to a5. Then, after the move b5-b6, Black would be unable to stop White from promoting a Pawn to a new Queen.
If we remove the a-Pawns from the diagram, then the b-Pawn is called an outside passed Pawn. Its distance from the mass of balanced Pawns on the Kingside (three Pawns against three Pawns) makes it an outside Pawn, and the lack of enemy Pawns on the way to its promotion square makes it a passed Pawn.
Returning to the diagram, we can't say that either White's a-Pawn or b-Pawn is passed, because the Black a-Pawn stands in the way. Instead we say that White has a potential passed Pawn, because the 2-to-1 Pawn advantage on the Queenside, also called a Queenside Pawn majority, guarantees that one of the White Pawns will eventually become a passed Pawn.
Outside passed Pawns are included in our discussion of elementary endgames because the challenges they present illustrate the strengths and weaknesses of the different pieces. Our guides in this discussion will be Yuri Averbakh, who analyzed basic positions in Chess Endings : Essential Knowledge, and Jon Speelman, who explored Averbakh's analysis in Endgame Preparation, adding his own basic positions. The diagrams are numbered according to those sources.
The simplest position is where only Pawns remain. The plans for both sides are straightforward : the Black King must stop a White Pawn from promoting and the White King must assist its Pawns against the Black King. Let's look at the plan in detail, using the same position as above.
First the Kings approach the center.
1.Kf1 Ke7 2.Ke2 Kd6 3.b4 Kd5 4.Kd3
The Kings are in opposition and battle to avoid yielding to the other King. The only way to do this is by making Pawn moves.
4...f5 5.f4 g6 6.g3 a6 7.a4
Black has lost the battle and is in zugzwang. Now the Black King must give way.
7...Kc6 8.Kd4 Kd6 9.b5 axb5 10.axb5 Kc7
Now White sacrifices the b-Pawn with 11.Ke5 and wins by capturing the Kingside Pawns.
After 11...Kb6 12.Kf6 Kxb5 13.Kg7 Kc4 14.Kxh7 Kd4 15.Kxg6, the result is clear.
The following diagram is the same as the first diagram above, except one Knight has been added to each side.
The winning plan with Knights is similar to the Pawn-only plan, but takes longer to execute. Because the plan is so long, we have inserted several intermediate diagrams and given the position its own page.
The following diagram repeats the previous, the Knights replaced by Bishops. White's h-Pawn and Black's a-Pawn start on safe squares where they cannot be attacked by the enemy Bishop, and the Black King is one move further from the center.
Bishop vs. Knight
Although the Bishop and Knight are considered of equal value, the Bishop has an easier time dealing with an outside passed Pawn. It can cover both flanks simultaneously, while the Knight can only rush from one flank to the other in short hops.
The Queen and Rook offer new opportunities for the defense. These pieces can guard both flanks at the same time, switching between attack and defense instantly.
From this discussion, we start to perceive the truth behind the general rule : When ahead in material, trade pieces; when behind in material, trade Pawns.
More pieces on the board mean more opportunities for the defense. When both sides have only Pawns, the strong side wins easily. When each side has a Queen, the weak side can harass the enemy King with checks.
More Pawns on the board mean more opportunities for the attack. If we eliminate the Kingside Pawns from the diagrams on this page, White's winning chances disappear.