# Devious Ending Study

Reposted since no one solved it. If no one offers a solution by the end of the week (Friday), I will post it myself.

Nn6/8/6r1/8/K7/1P6/1R6/3k2N1 w - - 0 1

No. 1-11
Yancey_Ward

Editor

After white sacrifices the knight, the rest of the ending does border on being inhuman, but is understandable if you think about it. So, after 1.Kc3 Ra6 2.Kb4 Rxa8 3.Kc3 Ke1 4.Re2+ Kf1 5.Re8! Kg1 you have the winning position that can be verified by the Nalimov Tablebase. Whenever the black rook departs the a8 square, the black knight is lost at b8, so the ending is like a R+P vs R ending where the issue is not allowing the black king to close in on the upper left corner of the board. White must use the king to help his rook accomplish this, but the white king will have to be careful to not allow black to play a check from the a-file while preparing the right moment for the advance of b4.

Yancey_Ward

Editor

White has to sacrifice the remaining knight.

Alena

As far as I see white mustn't let black win the white pawn so the only move is Kc3. I got stuck at the fourth move.

Yancey_Ward

Editor

White's third move should be easy to spot.

Alena

Yancey,thanks to your hint I have found the two key moves.

1.Ka3 Ra6+
2.Kb4 Rxa8

I have no idea how to proceed next so far. It's a very challenging endgame for me. I will try to solve it.

Yancey_Ward

Editor

After I had worked on this for a couple of days, I gave up the serial analyses and tried to leap ahead to the winning positions to see which of those I could create. Here is the key one I found where white has conceded both knights in order to force black to capture at a8 and has pinned the black knight to the rook. Of all these positions where the black king is on a square on the 1st rank, only the position where the black king is on h1 is it winning rn1R4/8/8/1K6/8/1P6/8/7k b - - 0 1 it was from this position alone that I figured out how white forces a win from move 1. The first move is not obvious at all- I never once considered it for 2 days. How does white mount an attack on the black king itself to drive him all the way to h1while still setting up a position similar the one I gave with the FEN above? The main issue with mounting an attack on the black king is this- black has the potential initiative in attacking the white rook first with Kc1, which forces white to move the rook. How does white prevent black from playing Kc1- in other words, can white protect the rook while it sits on b2?\

Alena

Yancey, I was wrong. I didn't manage to solve this problem. I checked V-2 with the help of The Lomonosov tablebases and it is a draw.

Yancey_Ward

Editor

I intentionally left off the last three moves so that you could work out the problem with this line- it is easier to understand the problem that way.

Yancey_Ward

Editor

1.b4 Kc1
2.Ra2 Kb1
3.Rd2 Rg1
4.b5 Rg4+
5.Ka5 Rg5
6.Nc7 Nc6+
7.Ka6 Rg6
8.b6 Kc1 And I could never make progress from this point. Every variation I looked at led eventually to a drawn ending I could verify with the Nalimov Tablebase at some point.

Yancey_Ward

Editor

Since you seem to have access to the Lomonosov Tablebase, I would suggest you put the positions in V1 and V2 after move 4 into it to verify they are, in fact, forced wins for white. I went down this exact line 6 years ago with this problem, and could never untangle the positions. This was especially true after 4.....Rg4+. Below this comment you will see what I considered at the time the critical line in 1.b4, and I don't see it differently today, but I have never put any of the positions into the Lomonosov when it reached 7 men, so that is why I ask that you do so before expending anymore time on this line. Of course, the way you wrote your comment seemed to suggest you did at least check to see if it was winning, and if you did, you have busted this problem from 2010. My difficulties with 1.b4 and another first move I could prove was wrong cost me many hours of struggle, but the second line I studied did eventually point me in the right direction. In any case, here is the critical line I found in 2012 for 1.b4 without the side variations which I can include if you want to see them:

Alena

I gave up trying to solve this puzzle because I thought I tried all varitions. Today I decided to try it again.
I had an idea.I found key moves. I know that it is a winning position and I want to figure it out by myself (without help of The Lomonosov tablebases) later.

V-1

1.b4 Kc1
2.Ra2 Kb1
3.Rd2 Rxg1
4.b5 Rg7

V-2

1.b4 Kc1
2.Ra2 Kb1
3.Rd2 Rxg1
4.b5 Rg4+

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