The Wrong-Coloured Bishop: Fortresses - Save A Lost Position

What is a Fortress?

A fortress is a defensive technique that one player, usually the defending side, implements to avoid losing. He/she does this in order to make it such that the opponent cannot make any progress ---- it is basically an unbreakable defense.

What is the Wrong-Coloured Bishop

Let's say you have just a king, and your opponent has an h-pawn and a light-squared bishop. If your king is close enough to the pawn, whatever white does, it will always be a draw. See the position below:

On first instinct it feels that white should be winning because there is an extra bishop and a pawn on the board. However, the pawn's promotion square, h8 is a dark square, while the bishop is a light-squared one. This means that as long as black is in the corner, anywhere on g8, g7, h7, or h8, white cannot really force it out of there. If white were to try, often the black king will be in stalemate. This is a fortress: though white is up 4 points of material there is no way of breaking black's defense of just staying in the corner.
Please note this only is applicable with a rook pawn. With central pawns this is a completely different story.

Sample Position

Consider the position above with white to move. White is down two pawns and with same-coloured bishops the game looks hopeless, not to mention the two black peepos are connected passers. However, there is an incredible way to save the game for white. Can you spot it?

Solution

Well white has the amazing resource Bh6!! Let's consider black's choices.
If black takes the pawn gxh6, then we get the wrong-coloured bishop scenario and white is happy. White's king is just going to stay in the g1-h1-h2-g2 box and there is no way for black to win. No matter if there is one pawn or there are 6 pawns on the h file black cannot win.
If black does not take the bishop you are ready to take the g7 pawn next, and the same scenario arises. Note that the g7 pawn is pinned so black cannot play g6. And so black is forced to go into a wrong-coloured bishop scenario and reluctantly give away 1/2 point.

Conclusion

This is it for this lesson on fortresses. We will examine more of these types with other imbalances. Stay tuned and see you soon!