An Unclear KBNPvKBP Fortress

I wrote this a few months ago because I was thinking about writing an endgame blog. That idea didn't go anywhere, but I might as well share this here because why not.

Today we will be analyzing a couple of positions in the KBNPvKBP endgame. To begin, I would like you to take a look at the position below and determine whether white can still win the game, or if black has successfully created a fortress.

Upon looking at this position, our dilemma is quickly apparent. The black pawn is placed on a square color opposite of our bishop, meaning our knight is the only piece that can capture the black pawn if it is defended by blacks bishop. However, if black were to then recapture our knight with their bishop, it would create a wrong colored bishop situation and lead to a drawn KBPvK endgame.

Now that we've determined that there is no obvious way to break the KBNPvKBP fortress, we must think outside the box to see if there is still some path to victory. And as it turns out, the position actually is winning for white! The secret is to capture the black pawn with discovered check.

The winning plan involves reaching a position like this or similar, and then picking up the pawn with discovered check. Note that if the black king attempts to run away from the corner in order to avoid the discovery, our dark squared bishop can block the black king out from the promotion square, thus leading to a winning KBPvK endgame.

Below is a position with a slightly different setup, taken from the final game between Tal Shaked and Alexander Morozevich at the World Junior Chess Championship in 1997. Tal Shaked, with the white pieces, successfully found the winning line and won the championship with a KBNvK endgame. This was a necessary victory for Tal Shaked to become the World Junior Champion - a draw would not have been sufficient.

This time, the black pawn is located along the 4th rank, not the 6th. However, the plan still works. Tal Shaked's first mission was to maneuver the king with Kg5-g6.

With the black king successfully boxed in and blacks bishop unable to stop white from progressing, Tal then shifted his bishop around to f7 with Be4-c6-e8-f7.

Now that the black king was successfully stuck in the corner, all that was left to do was a little maneuvering to set up the Ng6-h4 fork and discovery. Play continued Nd4-f5.

And now, white freed up the g6 square for the knight by retreating the bishop to c4 and following up with Kf7.

From here, all that is left to be done is place the bishop along the b1-h7 diagonal and then we are in position to make the discovery. (Side note, if black had played Kh7 in the above position instead of Be1, Bd3 would force Kh8 due to the threat of Nxh4+, leading to the same position as the one shown below.)

From here, Tal Shaked played Ne7-g6-h4 and won the game in classy KBNvK fashion after black sacrificed their bishop for whites h-pawn. Sauce.