Rook vs Bishop Endgame Imbalance

Introduction

This endgame imbalance involves one side having a rook while the other side has a bishop. No pawns are involved. Unlike Rook vs Knight, Rook vs Bishop is much easier to hold, due to the long range mobility of the bishop and its ability to make waiting moves. Rook vs Bishop is a theoretical draw, but as the defending side, it must be played precisely. See the position below, which is a possible way this endgame could come up. Please note that the attacking side has really only 50 moves to make any attempt at winning this.

Defending Side - How to Draw

Step 1: Choosing the Right Corner

Of course, the best strategy would be to hang out in the centre if possible, with the bishop close by. Do not get into any pins or forks unnecessarily; always be careful with every move. More often than not the attacking rook will manage to cut the king off and push it to the back rank. If this is the case, it is important to head to the right corner.

The king must head to the corner opposite to the colour of the bishop. For example, in the position above white's bishop is a dark square bishop, so the white king must go to h1 (easier) or a8. This is so that the bishop can easily block checks on g1 and h2. Just know that if you go to the wrong corner black will win easily.

Step 2: Just Wait with the Bishop

This endgame is easier to play out because white has a long range piece. Below is a position that could arise if white goes to the correct corner.

The king is on h1, and the bishop is a dark colored bishop, so it is perfect. Now, you will wait with the bishop along either the h2-b8 diagonal or g1-a7 diagonal. The rook can never really checkmate on the back rank as Bh2 or Bg1 will always be there.
In this position, white must be careful and play Bc7 so that Rh5+ is met by Bh2. If the black king tries to maintain the set up then white is left in stalemate. If White is not careful and plays Ba7 for example Rh5# is mate on the spot.

Tips for the Attacking Side to Win

Really the only way to win is to either:
- Hope for a fork/pin/skewer to win the bishop for free.
- Hope that the opponent blunders checkmate.
- Hope that the king goes to the wrong corner.

The third of these cases is much more likely. Examine the position below with black to move.

Black is winning if Black plays Kb3! We see that the king is near the wrong corner, as it is the same colour as the bishop. After Kb3 white has several possibilties, all of which fail.
- 2. Bf6 Rh1# (or if any other bishop move on that diagonal it will be the same mate in a few moves).
- 2. Bc1 Rh1 (zugzwang) 3. Ka1 Rxc1#
- 2. Ka1 Rh1+ 3. Bc1 Rxc1#
- 2. Kc1 Rh1+ 3. Kd2 Kxb2 -+

Conclusion and Further Practise

This endgame is not easy to master at first glance. This blog covers the main points to look out for. As always, like and comment if needed. Make sure to practise with the computer often, giving yourself both sides to see if you can draw or win accordingly. You only have to play 50 moves :)

Thank you for making it this far! I will link the study so that you can look at it. Hope to see you in my next blog post!

https://lichess.org/study/w41QzYTF/rsnbCZP9
https://lichess.org/study/w41QzYTF/xZxpHhEi