"All instruction books warn of too many pawn moves in the opening. In this category is the move h6--enthusiastically played mostly by beginners, but often enough also by experienced players."
After noting that h6 is not "of itself" bad, Diemer goes on to enumerate its drawbacks:
1) It loses time and neglects development.
2) It weakens (often decisively) the field g6.
3) After Black castles Kingside, it offers White the opportunity to tear open the position through a g2-g5 pawn storm, or through a sacrifice on h6.In the article I noted that h7-h6 appears frequently in the Euwe Defense, a natural reaction to White’s placing his Bishop on g5. The other day I came across a new game that reminded me of this article. It’s from a blog, called Korch Chess, which is worth a visit. The link is at the end of this post. Korch (2017) - Viner (1942) 16 min rated, Playchess, 10.07.2009 BDG, Euwe Defense 1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 exf3 5.Nxf3 e6 6.Bg5 Be7 7.Bd3 h6 8.Bh4 8...a6 [In a (fondly remembered) correspondence game from thirty years ago my opponent played 8...Nc6 here. See Purser-Carra below.] 9.0-0 Nc6 10.Kh1 g5 11.Bg3 Bd6 12.Ne5 Nxd4 13.Ne4 [Korch remarked that he missed 13.Bg6! After 13...fxg6 14.Qxd4 Black hurts for a good move. Note that if Black’s h-pawn were still on its original square Bg6 would not work.] 13...Nf5 14.Nxd6+ Qxd6 15.Rxf5 exf5 16.Nxf7 Qf8 17.Nxh8 f4 18.Ng6 Qc5 19.Qe2+ Kf7 20.Bf2 Bg4 21.Ne5+ Kf8 22.Bxc5+ 1-0 I was living in Germany when this next game was played in a postal tourney of the Rheinland-Pfalz Schachbund. The tourney, a Blackmar-Diemer thematic, was organized by longtime BDG-devotee Viktor Kuntz, who died shortly after it began. Purser,Tom – Carra Correspondence, Germany, 1979 BDG, Euwe Defense 1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 exf3 5.Nxf3 e6 6.Bg5 h6 7.Bh4 Be7 8.Bd3 Reaching the same position as in the previous game. 8...Nc6 9.Qd2 Nb4 10.0-0 Nxd3 11.Qxd3 0-0 12.Ne5 Nd5 13.Bxe7 Qxe7 14.Ne4 Nb4 15.Qg3 Nxc2? 16.Nf6+ Kh8 [And again, White’s next move was made possible by the weakening h7-h6.] 17.Qg6! gxf6 [17...Qxf6 18.Rxf6 fxg6 19.Rxf8+ Kh7 20.Rc1 (Another interesting line is 20.Nf7 g5 21.Rf1 Ne3 22.Rh8+ Kg6 23.Ne5+ Kh5 24.Rf3 g4 25.Rxe3) 20...Nxd4 21.Rxc7+-] 18.Qxh6+ 1-0 [18.Qxh6+ Kg8 19.Rf3 and mates.] Play through the games and download PGN here. Visit Korch’s blog here.