DEATH TO THE BLACKMAR DIEMER GAMBIT!!
It was with great interest that I followed this Blackmar Diemer Gambit debate, if only for the reason that this marginally playable line seems to have acquired and continues to acquire a dedicated and unshakeable following.
To convince an adherent of the BDG that it is unsound, is like trying to convince a child that there is no Santa Claus. Furthermore the chess literature that does exist on this opening is generally highly biased towards white, while other sources tend to be too vague or superficial in their analysis to be of much help to advocates of the black side. For instance many sources end their analyses after move 9 or 10 with an assessment of slightly better for black or clearly better for black, however while this maybe objectively true, this assessment does nothing to help black cope with the considerable initiative that white may generate against half hearted defence.
No wonder then that the BDG despite its poor theoretical reputation continues to wreak havoc at club level, and occasionally at master level as well. This trend is likely to continue unless you are lucky enough to be a member of this forum and reading this right now!
There are three ways to meet a gambit 1) Acceptance 2)Decline 3)Counter Gambit and the method chosen is largely a matter of taste, however, I have noticed that gambiteers and BDG specialists in particular hate to defend and for this reason I think the third method listed is the most unpleasant for them to face. Having said that it is my contention that black can take the offered pawn with impunity, nevertheless the line I am recommending here is a combination of both the second and third methods, with the added bonus that it offers strong counterplay without gambiting a pawn (Sounds cool doesn't it 8)). The line in question is called the O'Kelly defence, and in my opinion it is one of the best counters to the BDG, it also has the added benefit of being able to be used by Caro Kann players. Ok, that's enough hype don't you think, now its time to get to work

.
The following two games along with the accompanying analysis will equip you to face your next encounter against the dreaded BDG with confidence and conviction

, and for white players attempting to refute my analysis (Good luck you'll need it!

) you have my condolences
[Event "Bosna SuperGM"]
[Site "Sarajevo BIH"]
[Date "2000.??.??"]
[White "Short, N"]
[Black "Bareev, E"]
[Round "3"]
[Result "0-1"]
[WhiteElo "2683"]
[BlackElo "2709"]
[ECO "B10"]
1. e4 c6 2. Nc3 d5 3. d4 dxe4 4. Bc4 Nf6 5. f3
b5!? (This is an interesting choice, but black has other worthy alternatives:
A)5...exf3 6Nf3 Bf5 7Ne5 e6 80-0 Bxc2! This may seem greedy, but it works.

(8...Bg6 is also fine 9 g4?! overly ambitious but thematic for white 9....Nbd7 10Nxg6 hg6 11g5 Qc7! 12Bf4 Bd6 13gf6 Bxf4 14gf7 Be3+ and white resigned in Porrasmaa vs Lobzhanidze).
A1)9Qxc2? Qxd4+ -+ Winning
A2)9Nxf7 Kxf7 10Qg4 Qd7 11Bg5 b5!-/+ Black is clearly better.
A3)9Qe2!? Bg6 10d5 Bc5+ 11Kh1 cxd5-+
B)5...Nbd7 is the safe an reliable alternative 6Nxe4 (6fxe4 e5 7Nf3) 6....e6 7Ne2 Be7 80-0 Qb6 9Kh1 0-0 10c3 c5 11dxc5 Nxc5 12Nf6+ Bxf6=
C)5...e5 Unambitious but playable, giving back the material for rapid development 6dxe5 Qxd1+ 7Kxd1 exf3 8Nxf3 Ng4 9Ke2 Nd7 10Bf4 Nb6 11Bb3 +/= slightly better for white, but nothing terrifying.) The rest of the main game has already been analysed on chesspublishing.com by Aaron Summerscale and I have nothing to add to those comments, should you wish to see that analysis I highly reccomend you take out a subscription, its well worth it (Can't get everything for free

).
6. Bb3 e6 7. fxe4 b4 8. Nce2 Nxe4 9. Nf3
Ba6 10. O-O Bd6 11. c4 bxc3 12. bxc3 Nd7 13. Qc2
Nef6 14. c4 O-O 15. c5 Bc7 16. Bg5 h6 17. Bh4
Qc8 18. Rfe1 Bxe2 19. Rxe2 Nd5 20. Rf1 Qa6 21. Re4
Rae8 22. Rfe1 N7f6 23. Bxf6 Nxf6 24. Rh4 Qa5 25. Re2
Re7 26. g3 Rb8 27. Kg2 Rbe8 28. Qd3 Nd5 29. Ne5
Qc3 30. Qxc3 Nxc3 31. Rd2 Bxe5 32. dxe5 Nd5 33. Ra4
Rb8 34. Ra5 Kf8 35. Kf3 Reb7 36. h4 Ke7 37. Rd4
f6 38. exf6+ gxf6 39. Rda4 Nc3 40. Ra3 Nb5 41. R3a4
Rd7 42. Bc4 Nc3 43. Ra3 Nb1 44. R3a4 Nd2+ 45. Ke3
Rg8 46. Be2 Rxg3+ 47. Kf2 Rc3 48. Rxa7 Ne4+ 49. Kg2
Nxc5 50. Rxd7+ Kxd7 51. Ra7+ Kd6 52. a4 Rc2 53. Kf1
Ke5 54. a5 Kf4 55. Rg7 Ne4 56. Bd3 Ra2 57. a6
Nd2+ 58. Kf2 Nf3+ 59. Be2 Nd4 60. Rg4+ Ke5 0-1
The following game began as a Richter Veresov Attack, but I have altered the move order so as to include some pertinent analysis, I hope you don't mind.
[Event "?"]
[Site "Baku"]
[Date "1972.??.??"]
[White "Alburt, L"]
[Black "Tal, M"]
[Round "7"]
[Result "0-1"]
[ECO "A45"]
1. d4 Nf6 2. Nc3 d5 3. e4 dxe4 4f3 c6!? White now has many options, none of which offer any advantage:
A)5Nxe4 Nxe4 6fxe4 e5 7Nf3 exd4 (7..Bxe6!?) 8Qxd4 Qxd4 9Nxd4 Bc5 =/+ Black is slightly better.
B)5fxe4 e5 6Nf3 ed4 7Qd4 (7Nd4 Bb4 8Bc4 0-0 =/+) Qd4 8Nd4 Bb4 9Bd3 0-0 =
C)5Be3?! exf3 (The passively placed bishop on e3 makes this capture even more attractive than usual)
C1)6Nxf3 Bg4 7Bc4 e6 80-0 Nbd7 9Qe1 Bxf3 10Rf3 Bd6 -/+ Black is clearly better, with a possible follow up being Nb6-d5 with the further Qc7 and 0-0-0 in the offing.
C2)6Qxf3 Bg4 7Qg3 e6 8Be2 Bd6 9Qh4 Bxe2 10Ngxe2 Nd5 -/+ and once again black has consolidated his extra pawn.
D)5Bf4 Qa5 (5...ef3!?) 6Bc4 Nbd7-/+ Intending e5.
Now back to the main game
5Bg5 Nbd7! 6. fxe4 e5 7. dxe5 (7d5 Bc5 and 7Nf3 exd4 8Nxd4 Bb4 9Nf5 0-0 10Bd3 Ne5 11 Bxf6 Qxf6 120-0 Bxf5 13Rxf5 Qe7, Schiller-Ligterink 1986 are both good for black)7....Qa5 8. exf6?!
A)8Bxf6 gf6
A1) 9ef6 Nxf6 10Qd4 Bg7 110-0-0 0-0 12Nge2 Be6=/+ intending Rd8 with a good game
A2)9e6 fxe6 10Bc4 (10Qg4?! Ne5 11Qh5+ Ke7, intending 12...Nd3+ Winning the white Queen

) 10...Bb4 11Ne2 Ne5 12Bb3 Bd7 intending 0-0-0 with an excellent game.
B)8Nf3 Nxe4 9Bd2 Nxd2 10Qxd2 Bb4 110-0-0 0-0 12a3 Bxc3 13Qxc3 Qxc3 14bxc3 =/+
8....Qxg5 9. fxg7 Bxg7 10. Qd2 Alterternatively,
10Nf3 Qe3+ 11Be2 Bxc3+ 12bxc3 Qxc3+ 13Nd2 Ne5 140-0 Be6 15Nf3 Rd8 16 Qe1 Nxf3+ 17Bxf3 Qxe1 18Rfxe1 Rd2 19Re2 Rxe2 20Bxe2 Ke7 21 Kf2 Rg8 22h4 Kd6 and black was on the verge of victory in Elina-Chiburdanidze USSR 1976.
10...Qxd2+ (Black's initiative persists into the endgame, in particular his unopposed dark squared bishop raking the open board and white's exposed king more than compensate black for his pawn minus)
11. Kxd2 Nc5 12. Bd3 Be6 13. Nf3 O-O-O 14. Ke2 b5 15. a3 a5 16. h3 Rhe8 17. Rhd1 f5! (The rest of the game is a testament to the power of the bishop pair on an open board. Enjoy) 18. e5 Nd7 19. Re1 Bxe5 20. Kf2 Bf6 21. Re3 Nc5 22. Rae1 Kd7 23. Nxb5 f4 24. Re5 Nxd3+ 25cxd3 cxb5 26. Rxb5 Rb8 27. Ne5+ Kd6 28. Rxa5 Bh4+ 0-1
I hope those that have digested my contribution have enjoyed it, you better, as I am not in the habit of giving away this kind of Top Secret (and TopNotch

), highly classified knowledge for free( Kidding

). You are now equipped with an effective and deadly weapon against the BDG, all that is left now is for you to rip your next unsuspecting opponent limb from limb.
Your feedback to this post would be most welcome, so till then, may the force be with you.
Regards,
TopNotch