Pure opposite colored bishop endings are tricky things. They are rightly considered to have strong drawing tendencies, for a variety of reasons. The noted authority on endgames Mark Dvoretsky observes that “it is frequently possible to save oneself even two or three pawns down.” This is largely because of what he calls the main theme of an opposite colored bishop ending: The fortress. “The weaker side strives to create one, the stronger side strives to prevent its formation, or (if it already exists) to find a way to break through it.”
In simple terms, this is largely because the attacker cannot offer to exchange the defender’s bishop, nor can they compete with them for control of their color square. Imagine that the defender controls the square in front of a passed pawn with both their king and bishop: The attacker will need a diversion somewhere else on the board to give them to give way. As a result, many winning plans in opposite colored bishop endings involve creating passed pawns on opposite sides of the board, so as to overload the opponent’s defenses.
We will join a game between Jan Wolak and Karol Leszczewicz, from the semi-finals of the 2025 Polish Championship. Both players have FIDE ratings in the 1900s. Here Black has just played …Kb2, attacking White’s a-pawn. A pure opposite colored bishop ending is on the board, where Black is playing for a win – he has a passed pawn on f4 and is about to win a pawn on the queenside – and White plays for a draw. White has a deceptively tricky choice to make: Give up the a-pawn or the b-pawn?
43.a4! Would answer the call correctly – White needs to keep the a-pawn and give up the b-pawn. 43…Kxb3 44.Bb5 brings up the following position.
Ideal Drawing Formation
White’s pieces cooperate perfectly in their defensive tasks: The king blocks the passed f-pawn, while the bishop protects the queenside pawns. This shows an interesting strategic property of pure opposite colored bishop endings: The classical principle of keeping your pawns on the opposite color of your bishop only applies to the attacker! The defender actually wants their pawns on the same color as the bishop, so it can protect them. Note that it would not serve White to have their king and bishop switched: The king is a better blockader of a passed pawn, since it cannot be attacked and thereby pushed away by the enemy king.
Because Black cannot make a passed pawn on the queenside, he has no way to make progress.
Returning to the original position:
43.b4! would also have been fine. 43…Bxb4 44.a4 leads to the same situation described above, where Black has no way to create a passed pawn on the queenside and no way to dislodge the white queen from blocking the kingside passed pawn.
In the game, White played the natural looking 43.Ba4?, giving up the a-pawn instead. Black naturally captured it with 43…Kxa2, and White responded with the neutral 44.Ke2, bringing up the following position. Before you scroll below the position, try to come up with the winning plan for Black!
Winning Plan
Unlike in the situation where White retained the a-pawn, Black has an unstoppable plan to win a pawn on the queenside, thereby creating a second passed pawn. The plan is as follows:
1) Play …Ka3, …Kb4, and …a6. At this point …b5 will be threatened, trapping and winning White’s bishop.
2) White will have to move their bishop away, at which point Black plays …Kxb3, creating a passed a-pawn.
44…Ka3! Showed that Black understood the winning plan. Rather than wait for Black to carry it out, White decided to abandon the b3-pawn immediately with 45.Bb5, intending to use the bishop to block the a-pawn. Play continued 45…Kxb3 46.Ba6
White’s problem is that Black has succeeded in creating passed pawns on both sides of the board. His king cannot rush to the queenside to fight against the a-pawn, since Black would promote the f-pawn. He is trying to use his bishop to block the a-pawn, but we already know bishops are not good blockaders when they lack assistance from the king: The enemy king can simply attack and dislodge them. That is what happens here: 46…Kb4 47.Kf3 Ka5
Now if White tries 48.Bb5, Black will simply eject the bishop with 48…a6. Then after 49.Bc6 Kb4, the a-pawn can begin marching ominously down the board. So White went for the tricky 48.Bb7. Now the king stands in the a-pawn’s way, and 48…Kb4 49.Ba6 would just repeat the position. Unfortunately, it is a small matter for Black to start pushing the passed a-pawn. He chose 48…b5, when 49.cxb5 Kxb5 prepared the march of the rook pawn.
The subsequent play shows the way a king and bishop can be overloaded by passed pawns on opposite sides of the board. White seems to be holding on, until he cannot stop both passers. 50.Ke4 White tries to bring the king over to resist the a-pawn. 50…a5 51.Kd3 Kb4
52.Bd5 White can only wait. Here he tries to place his bishop where it controls the path of both pawns. 52…a4 53.Kc2 a3 54.Kd3
The Breakthrough
White has attempted to set up a fortress. Superficially, he appears to have been successful. The bishop controls the squares in front of both passed pawns, while the Black king cannot invade White’s position. However, 54…f3! breaks through decisively, showing that the White bishop ‘cannot dance at two weddings at once.’
If White takes on f3, the a-pawn advances safely to a2, with unstoppable promotion. So he tried 55.Kc2 f2 56.Bg2, when the king is (temporarily) stopping a-pawn and the bishop is controlling the f-pawn.
56…Bd4 threatened …a2, with unstoppable promotion, so White responded 57.Kb1. Try to find the immediate win for Black before going to the end of the diagram!
If Black immediately plays 57…Kb3, to threaten …a2+, White responds 58.Bd5+!, pushing away the Black king. When it returns, for example 58…Kb4, the Bishop returns 59.Bg2, once more protecting the queening square. So Black needs a preparation move before …Kb3. 57…f1=Q+! finishes the game. Only after 58.Bxf1 will Black play 58…Kb3.
By forcing the bishop onto the less desirable f1 square, Black has made it impossible for White to give a safe check. He is therefore helpless against the threat of …a2+ and then …a1=Q. White resigned a couple moves later.
Key Ideas
1. 43.a4! Kxb3 44.Bb5 would have created the ideal drawing formation for White: The king blocking the enemy passed pawn, with the bishop protecting the pawns on the other side.
2. Creating passed pawns on both sides of the board is a key way to break a fortress in an opposite colored bishop ending. 44…Ka3! started the winning plan of …Ka3-b4, …a6, and finally …b5, which would trap the bishop. The white bishop moved away to avoid this, but that allowed Black to capture on b3 and create a passed pawn on the queenside.
3. 54…f3! expressed the idea that the bishop cannot “dance at two weddings at once”, overloading its defensive abilities.
4. 57…f1=Q+! was a critical deflection, not allowing the bishop to check the black king away from cooperating with the a-pawn and black bishop.