K,R,P vs K,R

I found this position whilst training against endgamebot on FICS. The single, key winning move here has me thoroughly doubting my understanding of Lucena. Could anyone explain?



White to move and win in 20

kf6?

Originally posted by dzhafner
kf6?

I think Kf6 won't make any progress because of rook checks.

Rg4 I think...right?

Originally posted by pootstick
I think Kf6 won't make any progress because of rook checks.

I've only studied the basic Lucena position, so I don't think I can really explain this example. But the online Shredder endgame tablebases also indicates that, while Kf6 doesn't mate in 20, it does mate in 22.

http://www.shredderchess.com/online-chess/online-databases/endgame-database.html

Originally posted by Mad Rook
I've only studied the basic Lucena position, so I don't think I can really explain this example. But the online Shredder endgame tablebases also indicates that, while Kf6 doesn't mate in 20, it does mate in 22.

http://www.shredderchess.com/online-chess/online-databases/endgame-database.html

Yeh; I expect the two extra moves repeat the position. The thing is, the only move that makes progress doesn't really fit with any theory I know of - any high-raters or endgame specialists out there?

edit: c guy, if you follow Mad Rook's link it shows that Rg4, although natural-looking, draws.

You know that the Black Rook can safely give side checks as the Rook and pawn are separated by more than two lines [after Black plays 1. ... Ra8]? That is the main issue in this position.

Originally posted by pootstick
I found this position whilst training against endgamebot on FICS. The single, key winning move here has me thoroughly doubting my understanding of Lucena. Could anyone explain?

[fen]2r4k/5P2/8/4K3/8/8/8/6R1 w - - 0 1[/fen]

White to move and win in 20

This isn't really anything to do with the classical Lucena position. White achieves a win through a tactical device, namely 1.Rg6! with the idea of playing the rook across the sixth rank to face the opposing rook (e.g. 1...Ra8 2.Ra6!). Then Kf6, Rd6, and Rd1 wins, since the pawn can now be forced home.

Originally posted by Northern Lad
This isn't really anything to do with the classical Lucena position. White achieves a win through a tactical device, namely 1.Rg6! with the idea of playing the rook across the sixth rank to face the opposing rook (e.g. 1...Ra8 2.Ra6!). Then Kf6, Rd6, and Rd1 wins, since the pawn can now be forced home.

I agree. But white needs a forcing move to prevent Kg7 by black before he can make Kf6. It could go: 1.Rg6! Kh7 2.Rc6! Rb8 3.Kf6 and later on Rd6 followed by Rd1 (or Rd2, Rd3, Rd4). The same happens after 1.Kg6 Rb8, then white simply plays 2.Rb6! etc...

Originally posted by Northern Lad
This isn't really anything to do with the classical Lucena position. White achieves a win through a tactical device, namely 1.Rg6! with the idea of playing the rook across the sixth rank to face the opposing rook (e.g. 1...Ra8 2.Ra6!). Then Kf6, Rd6, and Rd1 wins, since the pawn can now be forced home.

I get that facing off the rook looks to force a Q v R ending, but I don't understand the thinking behind why necessarily from the sixth rank.

I'm also nonplussed about 4.Rd6 in Mephisto's line. Does it prepare a kind of sideways bridge, or could you please briefly explain the supporting logic?

ps. the diagram posted is from three moves after a lucena-ish position.

1. Rg6
Better than 1.Rc1
then black has two possibilities:
1. .. Kh7 or
1. .. moving around with the Rook on 8
The second one is easy: Just R to the same
as black's rook followed by Kf6
The first one:
2. Rc6 and then Kf6

Edit: ok, just saw the link to shredder. It seems more complicated,
than I thought

Originally posted by pootstick
I found this position whilst training against endgamebot on FICS. The single, key winning move here has me thoroughly doubting my understanding of Lucena. Could anyone explain?

[fen]2r4k/5P2/8/4K3/8/8/8/6R1 w - - 0 1[/fen]

White to move and win in 20

I have no idea about the position, but how do you "train against" endgamebot at FICS?

and may I state, that I'm really sick of not knowing how to overcome very simple tasks in FICS, is there a good manual or something?

tell endgamebot help

Originally posted by pootstick
I get that facing off the rook looks to force a Q v R ending, but I don't understand the thinking behind why necessarily from the sixth rank.

I'm also nonplussed about 4.Rd6 in Mephisto's line. Does it prepare a kind of sideways bridge, or could you please briefly explain the supporting logic?

ps. the diagram posted is from three moves after a lucena-ish position.

Let's give a line to make sure we are talking about the same things:
1.Rg6 Kh7 2.Rc6 Rb8 3.Kf6 Ra8 4.Rd6. Let's assume black replies with Kh6 (a move rook on the 8th rank instead doesn't change much).

White's plan is to get his king to e7 or e8 and promote the pawn. The rook on the d-file can block checks by black's rooks on the 8th rank. However, white can't just play 5.Ke7 because 5. ... Kg7 would draw. With 5.Rd1 (/2/3) he threatens checkmate on the h-file, forcing either
- 5. ... Kh5 after which 6.Rg1 Kh4 7.Kg7 wins
or
- 5. ... Ra6+ 6.Ke7 wins

Originally posted by heinzkat
tell endgamebot help

I will tell him that! (thanks 🙂)