13 September 2018

A Remarkable Tool

In my previous post, An Important Seven-piece Endgame, I discussed endgames of the type R+2P vs. R+P as given in 'Rook Endings' by Levenfish and Smyslov. I ended the discussion with:-

Despite the supposed simplicity of the other examples, I discovered a number of inaccuracies in their analysis. I'll discuss one or two of them in a future post.

Unlike the era of Levenfish and Smyslov (L&S), these endgames are now completely transparent thanks to the use of tablebases (TB). Consider the position in the top diagram below (Furman - Kopaev, event/year not specified). The TB gives 1.g5 as the only move, which is also the first move that L&S give. They wrote,

A strong move, opening up the White King's path to h5. It also makes it more difficult for Black's Pawn to advance.

Both sources agree that White has a won game and give 1...h5 as the best continuation for Black. L&S first examine 2.Rh6, where White wins the h-Pawn by force: 2...Rb2+ 3.Kg3 Rb3+ 4.Kf2 Rb2+ 5.Ke1 Ke3 6.Kd1 Kd3 7.Kc1 Rh2 8.Rxh5. The poor positions of the White Rook and King allow Black to draw with 8...Kc3 9.Kd1 Kd3 10.Ke1 Ke3 11.Kf1 Kf3 12.Kg1 Rg2+ 13.Kh1 Kf2 forcing perpetual check. (To follow the analysis in this post on Lichess, use the link below the diagrams.)

Lichess: 8/7p/5R2/8/4k1PP/1r6/6K1/8 w - - 0 1

The bottom diagram shows the position after the correct move 2.gxh6 (e.p.), followed by 2...Rb7 3.Kg3 Ke5. L&S now give the incorrect 4.Rg6, followed by 4...Kf5 5.Rg5+ Kf6 6.Kg4 Ra7 7.Kh5 Rf7 8.Rg6+ Ke7. Here Black can draw with 8...Kf5 9.Rg7 Kf6.

After 8...Ke7, L&S duplicate their error by giving 9.Rg7 Kf8, where 9...Kf6 leads to the same position (and the same draw) after 9...Kf6 in the previous paragraph. Instead of 9.Rg7, the continuation 9.Ra6 Rf8 10.h7 would win.

Back to the bottom diagram, instead of a draw with 4.Rg6, the TB says White should play 4.Rf8 Rh7 5.Kg4 Rxh6 6.Kg5, with mate in 64(!). This allows two conclusions: (1) the TB is a remarkable tool, and (2) not all Rook & a-/h-Pawn endings are drawn.

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