Monday 4 August 2008

A tricky Rook and Pawn Ending

One of the games at Street Chess on Saturday reached the diagrammed position. White realised that if he could move the rook and give a safe check to the Black king, then he would be able to promote. Black also new this, but then found the other way to lose (by moving the rook off the c file). The post-mortem then turned to whether this position was winning for White, with the in-expert consensus that it was.
But in trying to confirm this conclusion I found that it is probably drawn after all. Here are some simple (but direct) variations I came up with and although White has some wins if Black goes wrong (including a clever trick after the wrong 12tm move), correct play seems to hold. Nonetheless, feel free to correct me.

1.g4+ Kh4 2.Kg2 Rc4 3.Kf3 Kh3 [ 3...Rxg4?? 4.Rd8 is what happened in the game.] 4.Ke3 Kg3 5.Kd3 Rc1 6.Kd4 Kf3 7.Kd5 Kf4 8.Kd6 Rd1+ 9.Ke6 Rc1 10.Kxf6 And it looks as though White is easily winning. But what happens if the Black king continues to hide? 10...Rc3 11.Kg6 [ 11.Ke7 Kg3 12.Kd7 Rd3+ 13.Kc6 Rc3+ 14.Kd6 Rd3+ 15.Ke5 Rc3 16.Kd5 Rc2 also seems drawn, as the Black rook just checks to drive the king away from d6 or d7] 11...Kxg4 12.Kxh6 Rc6+ [ 12...Kh4?? 13.Kg6 Kg4 14.Kf6 Kf4 15.Ke6 Ke4 16.Re8!!+-] 13.Kg7 Kg5 14.Kf7 Kf5 15.Ke7 Ke5 16.Kd7 Rd6+ =

4 comments:

Anonymous said...

I think it is winning. I do not like your first move. There is a rule that if you have a pawn minority you should not push.

The plan is to take the f6 pawn without pushing the g pawn. Black's king will have to stay on h5 all the time. Then move white's king somewhere safe and push g4 and g5. Without the f6 pawn black can't take the g5 pawn by either the h pawn, or the king, or the rook.

Anonymous said...

The move I thought of was 1.g3. Now the Black King is stuck (any legal move loses to Rg8+) so apart from ...f5 Black can only slide the Rook on the c-file. White can now shift his King to the d-file and then d6 threatening to release the Rook so Black must play ...Rd1+ whereupon Ke6 wins the f-pawn on f6 or f5.

However White still has the problem of getting the Rook out, the f-pawn is not really the issue. Once the King is on the fifth or sixth rank it just gets checked from behind. The answer is to bring it all the way back to h3, threatening g4+ and Rg8+, But Black responds ...Rc3 and there is no zugzwang, White has no move to waste. The only trick I can see is Rg8, meeting ...Rxc7 with g4#, which looks good until you see ...Rxg3+ and either capture is stalemate.

BUT what about doing this without taking the f-pawn first so the stalemate trick doesn't work? I think Black can meet this by playing an early ...f5 and swapping the rook between c1 and c3, so that when White's King reaches h3 he has either ...Rh1+ or ...f4 however much White tries to triangulate.

If White doesn't push the g-pawn at all he will eventually have to transpose into 1.g3 or 1.g4 when he does. So I lean to thinking it's drawn.

Anonymous said...

On deeper thought, in the line where White doesn't win the f-pawn it wouldn't be good for Black to meet Kh3 with ...f4 becasue then Rg8 really does win (...Rxc7, g4#, or ...Rxg3+, Rxg3 and c8=Q). However with the pawn on f5 there is no mate threat so Black simply holds the c-file.

Anonymous said...

I think the solution is correctly described in my first post.
1) Take the "f" pawn.
2) If white checks then just approach the rook, eventually checks will stop.
3) Push g4 and g5.

I do not see what black can do against this somple plan.