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1.  Ragnorak
06 Nov '05 14:52
I haven’t found any online resource which spells out the ideas behind this mating pattern, so I have chosen to do so myself, after playing my engine in this endgame about 100 times in the past couple of weeks. I haven’t read about this mate anywhere, so I welcome any constructive criticism which betters this tutorial. I may not explained some parts as well as could be explained, so I’d appreciate any revisions that people would like to contribute.

Once you get to the B + N + K v K endgame, the starting positions of the pieces is irrelevant.

This mating pattern can be broken down into 3 phases:
1) Getting the enemy king to one of the edges
2) Forcing the king along the edge and into the corner with the same coloured square as your bishop, ie: if you have the light bishop, you need to move the enemy king towards a light squared corner.
3) Completing the checkmate.

TBC...

D
2.  Ragnorak
06 Nov '05 14:53
Step 1
The best way to get the king to an edge, IMO, is to use mostly the king and bishop, with the knight used to block the squares on which the King can escape to.

This method is great for getting the enemy king to the edge. Use your king to protect the bishop like this, which forces the enemy King 1 rank/file towards the edge.

Once the king moves away to d2 or f2, move the king and try to get the same position on the next rank/file closer to the edge. The knight will be needed to prevent the king from escaping if Black plays as expected.

So, the moves would look something like…
1. Be4 Kd2 2. Kd4 Ke2 3. Nd3 (prevents the king from escaping via f2) Kd2 4. Nf4 (prevents the King from escaping via e2)

These steps need to be repeated until the enemy king is on the edge. That completes Step 1.

TBC...

D
3.  Ragnorak
06 Nov '05 14:54
Step 2
Force the enemy King along the edge into the same coloured square as your bishop.
There is a fixed pattern for achieving this. You need to achieve a position something like this…

The important points about this position is that the knight is attacking a square which the bishop can’t attack, ie: the dark squared c1 square. The King protects the knight on the 2nd rank/file and also protects 2 dark squares which the light bishop can’t. The bishop prevents the king escaping via c2, so black is forced into playing …Ke1, a step towards the correct corner.

TBC...

D
4.  Ragnorak
06 Nov '05 14:55 / 1 edit
After 1…Ke1, use the light bishop to prevent the king from moving away from the correct corner again, so 2. Bc2, which forces the king a further square towards the correct corner with 2…Kf1. If you get this position further along the edge, then repeat these moves as necessary.

Now, the king doesn’t want to get stuck in the light coloured corner, so he would like to escape back into the centre of the board with Kg2, so use the knight to prevent this with 3. Nf4, pretty much forcing the King into 3…Ke1 as he wants to keep away from the light squared corner. 4. Ng2+ forces the king to move to 4…Kf1. Now, step 2 is almost complete. Move your king to 5. Kf3 to protect the knight while always keeping it on the 3rd rank/file. This forces the enemy king into 5…Kg2 and you can close the escape door again with 6. Bd3.

That completes Step 2.

The hard part about that step is getting the knight onto the correct square (on the 2nd/7th rank/file attacking the square on the edge which the bishop cannot) without allowing the enemy to escape back to the centre. If you achieve the position in the first diagram of step 2 of the post above this one, then the rest is quite forced.

TBC...

D
5.  Ragnorak
06 Nov '05 14:57 / 2 edits
Step 3.
Completing the mate in the same coloured corner as your bishop.

This is probably the easiest part of the mating pattern (with achieving the first position shown of step 2 the most difficult)

So step 3 starts off with this position.

The black king is left with 2 options, Kh1 or Kh2. Either way it is doomed.

1…Kh1 2. Kg3 Kg1 3. Nf4 Kh1 4. Bc4 (move needed to avoid stalemate) Kg1 5. Nh3+ Kh1 Kd5++

Kh2 is treated quite similarly, which I'll leave as an excercise. The basic aim for white is for your bishop to block 1 escape route, while using a combination of your knight and King to block the other. You need to use the knight to check the king back into the corner, and then deliver mate with the bishop.

And I think that is that. I'm willing to play a few games as the lone king to help people who want to play through the tutorial (thanks to Schakuhr doing this for me a while ago), so pm me or send the setup game, if you wish.

D
6. 08 Nov '05 00:58
check out ICC they have a very very nice lecture on this subject given by mrspock and you can practise it against one of the bots. Also this fisher site had a nice article on how its done. Thats how i learnt how to do it. Sort of useless. I only had that situation happen to me once a long long time ago.
7. 09 Nov '05 21:17
Originally posted by RahimK
check out ICC they have a very very nice lecture on this subject given by mrspock and you can practise it against one of the bots. Also this fisher site had a nice article on how its done. Thats how i learnt how to do it. Sort of useless. I only had that situation happen to me once a long long time ago.
Will be kicking myself if I come across the situation and I do not know how to do it (which I don't, so far).

Only useless until you need it.
8.  DeepThought
09 Nov '05 21:38
Originally posted by lausey
Will be kicking myself if I come across the situation and I do not know how to do it (which I don't, so far).

Only useless until you need it.
I've played over 600 games on this site, in one of them it was a possible outcome that didn't happen. I've never seen it OTB either. It's the kind of thing that comes up once in your life. The reason to study it is not so much for the one time it does come up, but because knowing how to do it will help your overall endgame technique. I've got too many games on at the moment, but I'm going to take Ragnorak up on his 'I'll defend it' offer at some stage.
9.  Ragnorak
15 Nov '05 12:13
Originally posted by DeepThought
I've played over 600 games on this site, in one of them it was a possible outcome that didn't happen. I've never seen it OTB either. It's the kind of thing that comes up once in your life. The reason to study it is not so much for the one time it does come up, but because knowing how to do it will help your overall endgame technique. I've got to ...[text shortened]... t the moment, but I'm going to take Ragnorak up on his 'I'll defend it' offer at some stage.
If you approach an endgame and you know this mating pattern, then you can specifically aim for it. Some opponents would be happy to test your knowledge of this endgame, thinking they might be able to get a draw out of it.

Also, its great practice for how the knight and bishop can work together.

I've had this situation come up 3 times in real games.

D
10. 15 Nov '05 23:32
thanks for this ragnorak
11.  Ragnorak
15 Nov '05 23:51
Originally posted by Ragnorak
This forces the enemy king into 5…Kg2 and you can close the escape door again with 6. Bd3.

D
12.  Marinkatomb
wotagr8game
18 Nov '05 17:37
Rag, you've out done yourself! Rec for you my son!!
13. 10 Jan '06 15:22
I'm beginning to work through this now. Sterling effort, Rag.
14.  Ragnorak