In our search for the refutation of the Blackmar Diemer, we come to a line that will surprise many as the defender deliberately plays an anti-positional move, blocking his centre.
In the Gunderam defense, black may surprise the attacker after 1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 exf3 5.Nxf3 Bf5 6.Ne5 c6 7.g4 and now, insteading of retreating to g6, black plays the anti-positional move 7...Be6 (diagram)
In my book "Attack with the Blackmar Diemer", I had suggested 8.Bc4, but this seems not optimal now, as black can get rid of his badly placed bishop and free his game after 8...Bxc4 9.Nxc4, eg 9...b5 10.Ne5 b4 11.Na4 and white's position resembles that of a complete beginner.
But what are the alternatives ? Let's look at 8.g5. Black has two reasonable replies : 8...Nd5 and 8...Nfd7.
a/ 8...Nd5 9.Ne4 (diagram)
Doesn't look good for white, does it ? Black has simple killer moves, such as Nd7 or g6 to develop quickly
b/ 8...Nfd7 9.Nd3 (diagram)
A strange position occurs. It looks like white's game is that of a complete beginner, with black also not doing very well... One thing is for sure - black has made less committing moves than white ! Na6 and g6 seem once again simple development moves that give black the advantage.
So dear BDG friends, how do you assess this line ? Scheerer had called 7...Be6 the main line, and his analysis confirmed that the lines are "quite solid for black, and it is difficult to find a clear way for the advantage for White here.". I would go even further and use the "R" word !