About half of these positions are drawn. In most other endings, a two-pawn advantage is usually an easy win. For comparison, if the bishops were on the same color squares, over 90% of the positions would be wins. There are three general cases, depending on the two pawns. In most endings, a pair of connected pawns have the best winning chances, but in these endings, a widely separated pair of pawns have the best chances unless one of the pawns is the
wrong rook pawn.
Doubled pawns With
doubled pawns, the position is a draw if the defending king can reach any square in front of the pawns that is not of the color of the attacker's bishop. The second pawn on the is of no help, so this is like the ending with only one pawn. If the defending king and bishop cannot accomplish this, the first pawn will win the defending bishop and the second one will
promote.
Isolated pawns With
isolated pawns (on non-adjacent files), the outcome depends on how widely separated the pawns are. The more widely separated they are, the better the winning chances. The rule that holds in most cases is that if only one file separates the pawns the game is a draw, otherwise the attacker wins. The reason is that if the pawns are more widely separated, the defending king must block one pawn while his bishop blocks the other pawn. Then the attacking king can support the pawn blocked by the bishop and win the piece. If only one file is between the pawns, the defender can stop the advance of the pawns. See the diagram. If three files separate the pawns, the pawns normally win. However, there are positions where the defender can set up a blockade, especially if one of the pawns is the
wrong rook pawn. In this position from
Yuri Averbakh, Black draws since the bishop can restrain both pawns on the same diagonal with the help of the king and the white bishop is helpless. :
1. Kd5 Kf6! The white king will not get to e6. :
2. Kc5 Ke7 :
3. Kb5 Bf4 :
4. Kb6 Kd8, draw. An example is the game N. Miller vs.
A. Saidy, American Open 1971. White in this position because he knew a "rule" articulated by
Fine in the first edition of
Basic Chess Endings: "If the pawns are two or more files apart, they win." Since here three files separate the pawns, White assumed his position was hopeless. However, the position is actually a fairly straightforward draw, since "White's King has such a powerful active location that he can keep Black's King from penetrating either side of the board.". Play might continue
1. Bh3+ Ke7 2. Bg2 Kf6 3. Bh3 Kg5 4. Bg2 Kf4 5. Kc4! Bd4 6. Kd3 Bg1 7. Bc6 Kg4 8. Bg2! Bf2 9. Kc4! Kf4 10. Kd3 Ke5 11. Kc4, when, "Clearly there is no way for Black to break the blockade."
Wrong rook pawn If one of the two pawns is the wrong
rook pawn (i.e. an a- or h-pawn whose
queening square is the opposite color from the squares on which the superior side's bishop moves), a
fortress may allow the inferior side to draw irrespective of how far apart the two pawns are. This is illustrated by
Alekhine–
Ed. Lasker,
New York City 1924. (complete game) Three files separate Black's two pawns, but the players
agreed to a draw after 52.Bb1 Kg7 53.Kg2. Alekhine explained in the tournament book that White "can now
sacrifice his Bishop for the [d-pawn], inasmuch as the King has settled himself in the all-important corner". If one of the pawns is the wrong rook pawn, it does not matter how widely separated or how advanced the pawns are. The outcome depends on whether or not the defending king can get into the corner in front of the rook pawn and sacrifice his bishop for the other pawn.
Recap Grandmaster Jesús de la Villa emphasizes the importance of this endgame and gives this breakdown depending on how many files separate the pawns: • If the pawns are separated by two files: • Two normally win • With a and a the position is usually a draw, but there are winning chances if the knight pawn is not far advanced and the attacking bishop controls its promotion square • with a and a central pawn the endgame is a draw • If the pawns are separated by three files: • With a knight pawn there are drawing chances if the pawn is far advanced • With a rook pawn the position is usually won • If the pawns are separated by four files :: The ending is won because the attacking king gets between the pawns.
Connected pawns Positions with
connected pawns are the most complex case, and the result depends on the and of the pawns and the colors and locations of the bishops. If one of the pawns is a (on the a- or h- file) the position is normally drawn. If the pawns are on the opposite color as the defender's bishop, the defender may be able to blockade the pawns and draw. If both pawns can safely reach the sixth rank, they win unless one is the
wrong rook pawn, i.e. the rook pawn that promotes on the square of the same color as the defending bishop. The ideal drawing setup is seen in the diagram at left. Black's king (on a square not of the color of the opposing bishop) and bishop stay two ranks in front of the pawns, with both defending against a pawn advance (here
d6 by White) to the same color square as the bishop. The defending bishop must maintain an attack on the pawn on the same color square as itself, so that the attacking king is not allowed to advance. If White the other (unattacked) pawn, Black's bishop itself for both pawns, with a draw. (If the second pawn is protected and advances instead, the position is also a draw.) In the diagram position, Black on move passes (i.e. a waiting move that maintains the attack on the pawn) with
1... Bb8! 2. Ke4 Bc7! 3. Kf5 Bb8! and so on. White cannot make progress:
4. d6+ is met, as always, by
4... Bxd6 5. exd6+ Kxd6 with an immediate draw;
4. e6 gives Black an unbreakable blockade on the dark squares; and White can never prepare for
d6+ by playing
Kc5 because Black plays
... Bxe5. A similar position with White's pawns on the sixth rank is a win because the black bishop has no room to move and maintain the attack on the pawn on d6, thus Black is defeated because of
zugzwang. In the position at right, Black loses immediately. Black, on move, must give way with either bishop or king, allowing White to move
e7, winning, or else play the hopeless
1... Bxd6 2. Kxd6. If White is to move in this position, he plays a waiting move such as
1. Kc6, placing Black in the same predicament (
1... Ke8 2. Kc7#). ==More pawns==