Ziegler Defense

The Ziegler Defense, 5...c6, is widely seen as Black's most testing answer to the Blackmar-Diemer Gambit, and most modern authors recommend it. It takes its name from Diemer's practice of naming lines after opponents who first used them against him, though Gerhart Gunderam did much of the analysis. The modest pawn move steadies the center, holding the extra pawn without committing the queen's bishop, which usually goes to f5 or g4 once White has developed. The engine gives Black a slight edge, yet White wins more often in online games.

The most common reply is 6. Bc4. The old main line 6...Bf5 7. O-O e6 8. Ne5 Bg6 leaves White with little for the pawn, while 8. Ng5, the Alchemy Variation, sets more traps on e6 and f7. Lev Gutman's 7. Bg5 e6 8. Nh4 Bg6 9. Nxg6 hxg6 10. Qd3 prepares queenside castling and pressure on f7, and 7. g4 offers a second pawn. The second choice, 6. Bd3, often follows 6...Bg4 7. h3 Bxf3 8. Qxf3 Qxd4 with sharp play. Black can avoid 6. Bd3 by playing 4...c6 first, the O'Kelly move order.