This morning I have been going through some games in the Spanish Opening (Ruy Lopez), Chigorin variation in which White opts to close the center. In many of these games, White attempts to exploit a space advantage (greater piece mobility) by building up an attack on the g- and h-files. Hence, I felt immediate revulsion when Black played 18...h5 from this position.
Black to move
The game that led to the diagram position:
Weber,Gerhard -- Geissert,Eberhard [C97]
DDR-ch 13th Aschersleben (17), 1963
1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.0–0 Be7 6.Re1 b5 7.Bb3 d6 8.c3 0–0 9.h3 Na5 10.Bc2 c5 11.d4 Qc7 12.d5 Re8 13.Nbd2 Bf8 14.Nf1 g6 15.Ne3 Bg7 16.Nh2 Kh8 17.b3 Rf8 18.g4
18...h5? 19.f3 Qe7 20.Ng2 Nh7 21.gxh5 gxh5?
Black's seemingly obvious move is identified by Stockfish 4 as the error that led to White's clear advantage. The engine perceives 21...Ng5 as Black's only move. My intuition traces the critical error back three moves to a weakening pawn thrust. The pawn exchange on h5 is a consequence of Black's plan to play into White's plans by facilitating action on the g- and h-files.
White to move
Now White is prepared to demonstrate the flaws in Black's plan. A temporary pawn sacrifice to open the center is a central part of the refutation.
22.f4 exf4 23.e5! Bxe5 24.Bxf4 f6 25.Qxh5 Rg8 26.Kh1 Bb7 27.Rad1
Black to move
Surely, White is better here.
27...Rg7 28.Bh6 Rg3 29.Nf4 Kg8 30.Rg1 Rg5 31.Bxh7+ Qxh7 32.Rxg5+ fxg5 33.Qxg5+ Bg7 34.Rg1 Qe4+ 35.Qg2 Bxd5 36.Nxd5 1–0