[Event "Hamburg"] [Site "?"] [Round "0"] [White "Kluxen"] [Black "Lasker"] [Result "0-1"] [ECO "D08"] [Opening "QGD: Albin, 4.a3"] 1. d4 d5 2. c4 e5 3. dxe5 d4 4. a3 Nc6 5. Bf4 Nge7 6. Bg3 Nf5 7. Qd3 { Too aggressive. Having lost time with a3 White shouldn't be weakening his back rank like this.} 7... Qg5 8. f4 {Weakening his king position.} 8... Qh6 9. Nh3 Ne3 10. Nf2 {The decisive error, missing the point of Black's maneuver.} 10... Bf5 11. Ne4 Bb4+ { A very pretty move, leaving White helpless against Black's knights.} 12. Nbd2 { 12.axb4 Nxb4 13.Qd2 Bxe4 14.Qxb4 Nc2+} 12... Bxd2+ 13. Kxd2 Qg6 14. Qb3 Bxe4 15. Bf2 Na5 { The queen can't escape in the variation: 15...Na5 16.Qb5+ Bc6 17.Qxa5 Nxc4+} 0-1