As a rule, you should never trade down to a king and pawn ending unless you are sure you know how to achieve the result that your are playing for. If you are playing for a draw, you better be sure that the king and pawn ending is drawn, and you better be sure that it's won if you are playing for a win. Otherwise, you are better off keeping pieces on the board.
Here is a perfect example from Prospect's match against Barrington. With rooks on the board, the ending was likely a draw even though White would be down a pawn, but the king and pawn ending with even material was lost for White.
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| Pos. 1 |
After 33. Kf4 bxa5 34. Re8+ Kf7 35. Rb8 Rb3, Black is going to find it very difficult to capitalize on his extra pawn.
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| Pos. 2 |
The problem for Black is how to get his rook out from in front his b-pawn without losing it once he gets the pawn close to queening as in Pos. 3.
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| Pos. 3 |
If the White king were on f3, Black could play 1...Rf1+ followed by 2...b1=Q. If the White king were on f2, Black would have the tricky 1...Rh1! 2.Rxb2 Rh2+! winning the White rook. However, if the White king stays on g2 or h2, or in front of its pawns on g4 or h4, the Black rook can't move without losing the b-pawn. That means that the Black king will have to come over to help, which will give the White king a shot at the Black pawns.
Unfortunately, White played
33. Re3? After
33...Rxe3e+ 34. Kxe3 axb5 35 Kd4 Kf7 36. Kc5 Kf5 37. Kxb5 Kf5, White got his pawn back but his position was dead lost because he could not stop the Black king from getting at his remaining pawns and his king is too far away to get at the Black pawns.
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| Pos. 4 |
Even if the Black pawn were a file closer on c5 as in Pos. 5, the position would still be lost for White.
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| Pos. 5 |
The problem for White is that it still takes him three moves to get to the Black pawn, which leaves him insufficient time to get back to protect his own pawns. After, 35 Ke4 Kf7 36. Kd5 Kf5 37. Kxc5 Black would just have to be careful to play 37...Ke5 rather than 37...Kf5 (as in Pos. 4) in order to prevent the White king from blocking the Black king's path with 38.Kd4.
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| Pos. 6 |
In order to be able to draw this ending, White would need the Black pawn to be
both a rank and a file closer on c4 as in Pos. 7.
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| Pos. 7 |
Now the White king has time to capture the Black pawn and to get back to block the Black king from getting to the White pawns. 35 Kd4 Kf7 36. Kxc4 Kf5 37. Ke3.
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| Pos. 8 |
Remember: Rook endings are notoriously drawish. Don't trade off a well placed rook just to win back a pawn unless you are sure that the resulting king and pawn ending is good for you.
