FSR: 3...c5 is weak. Instead, Black should develop with 3...Nf6 4.f3 (the famed Blackmar-Diemer Gambit) exf3 (4...Bf5!?, Shankland's preference, is about equally good). Now sacking a second pawn with 5.Qxf3? (the Ryder Gambit) Qxd4 6.Be3 Qh4+ 7.g3 Qg4 is totally unsound. So White continues 5.Nxf3, and now 5...c6! leaves Black up a pawn for very little. This line is recommended for Black by GMs Svidler and Gustafsson (separately), among others. It can also arise from the Caro-Kann, Fantasy Variation, if White plays it as a gambit. White usually continues with 6.Bc4 Bf5! 7.O-O e6 8.Ne5 (threatening both Rxf5 and Nxf7), when 8...Bg6! gives Black a huge advantage. The crazed 7.Ne5 e6 8.g4!? is a better try, but 8...Nfd7! (making way for ...Qh4+) is a strong rejoinder. Instead of 5...c6, GM Joe Gallagher advocates 5...g6, which is also good but more complicated. It is interesting that Svidler endorses 5...c6 in Part 2 of his Chessable Lifetime Repertoire course on the Gruenfeld (I was a beta tester), even though I would have expected him to plump for 5...g6 in a Gruenfeld course.
I am playing in a Blackmar-Diemer thematic correspondence tournament. After 5...c6, I played the abject (but Stockfish-approved) 6.h3 (a sad move after sacking a pawn) Bf5 7.Bd3 and generated enough play to draw in both F Rhine vs S Valladares Caron, 2024 and F Rhine vs J Polanik, 2024. I was surprised to learn from the engine that the BDG, though bad, probably does not lose with perfect play. Black gets around a -0.6 advantage, but not quite enough to win.
After 3...c5?!, 4.Bb5+ Bd7 5.dxc5; 4.Nge2 cxd4 5.Qxd4; and 4.d5 Nf6 5.Nge2 all give White at least equality, which is more than he deserves. 4.Bf4!? is objectively bad, but more swashbuckling, so it's understandable that Gedult, a coffeehouse player, preferred it. Black should respond with 4...cxd4! 5.Nb5 Na6! with a big advantage. But after the naive 4...Qxd4??, 5.Nd5! won material, so Black resigned.
Kibitzing
