HAJS wrote on 07/30/20 at 17:07:33:
To Stigma:
Based on my non-existent theoretical understanding about the Samisch, I would argue that 6.Nge2 looks less flexible compared to 6.Be3 unless we are indending to develop the bishop elsewhere. I could see how the knight might want to go to h3-f2 or h3-g5 etc. How does Barrish and others motivate their choice of 6.Nge2?
Barrish just writes about 6.Nge2:
"By not committing our dark bishop yet, we have the extra option of playing Bg5 sometimes."
Paddy wrote on 07/30/20 at 22:38:54:
Move orders:
6 Bg5 - I think Eric's book is still by far the best source, but some might like to view Andrew Martin's DVD in the Chessbase 60-minutes series; recent Modern Benoni sources should probably also be checked out;
6 Be3 - the older books all tend to focus on this;
6 Nge2 - loses some flexibility with this knight, but the argument is that, since it seems sound for Black to answer 6 Be3 with 6...c5, White might as well delay the development of the c1-bishop. As already mentioned, Dreev is the big specialist.
Via the 3 f3 move order, there is the extra option of delaying Nb1-c3 and instead playing Ng1-e2-c3; this is interesting but not necessarily an improvement.
My understanding of the 6th move issue is each of the three moves has advantages and disadvantages:
6.Be3 was the undisputed main line until around 1990, since everyone assumed it stopped 6...c5. But then several games by Shirov, Gelfand and others showed Black can gambit the pawn and get enough compensation, even with the Queens exchanged. White could play 6.Be3 c5 7.d5 instead and aim for a Benoni transposition, but the usual view is the bishop would have been slightly better on g5 in that case.
Both 6.Bg5, 6.Nge2 and
6.Be3 c5 7.Nge2 are attempts to solve this dilemma - the latter move order allows Black to transpose to a Maroczy Bind or continue to offer a Benoni structure, but with the knight forced to choose a square possibly a bit earlier than he would ideally have liked with 7...Nc6. Then 8.d5 Ne5 is standard and has developed a lot of sometimes razor-sharp theory, while 8.d5 Na5, which was little-known before 2010, is more experimental but has done well in practice. But even after 7...Nc6 8.d5 Ne5 there are lines where the bishop turns out to belong on g5, so White takes a tempo loss with Be3-g5.
I believe if Black promised not to play 6...c5 there would be no reason for White to avoid 6.Be3, as it overprotects the centre and is a great bishop placement in all lines except the Benoni lines. But the other moves also have their downsides:
6.Nge2 keeps the option of Bg5 in one move, but loses the option of playing Nh3, which is normally the ideal response to an early ...Nbd7 by Black, when ...Bxh3 is no longer possible - on h3 the knight avoids blocking White's other pieces and usually goes on to find a convenient home on f2. From e2 the the knight will have to move again to allow Bf1 to delevop, but each of the possible squares g3, c1 and f4 are also a bit awkward.
So if Black wants to try to exploit the downsides of 6.Nge2, it's logical to either go for a line with an early ...Nbd7 (i.e. the Byrne system or the Benko attempt with Nbd7/a6/c5/b5) or allow a Benoni but try to exploit White's usual Ne2-g3 by answering it with ...h5-h4 or the Fischeresque ...Nh5!?.
6.Bg5 gets the bishop to its best "Benoni square" immediately and as a bonus prevents 6...e5, a traditional main line against 6.Be3 (I still get 6.Bg5 e5?? 7.dxe5 dxe5 8.Qxd8 Rxd8 9.Nd5 +- sometimes in bullet or blitz). White isn't worried about 6...h6, since he will win that tempo back with 7.Be3 and a later Qd2. The downside is the centre and specifically d4 is a bit less secure than with Be3. I think if Black wants to exploit this he should try some of the many lines based on quick Queenside play with ...b5, since that may be more uncomfortable for White if his centre doesn't feel quite secure. There are many setups where Black plays or at least threatens ...b5: The Panno with Nc6, a6 and Rb8, the Byrne system with a6, c6 and Nbd7, the Benko attempt with Nbd7/a6/c5/b5, a recently popular move order covered by Vigorito on ChessPublishing with ...a6, Nbd7 and ...b5 as a pawn sac, etc. Well, this is my impression after dabbling in 6.Bg5 without ever learning the theory very well - I'm sure ErictheRed will correct my misconceptions!
So to turn the board around, Black can try to be crafty and play the main lines of 6.Be3 c5 but against 6.Nge2 and 6.Bg5 do something different to try to exploit their specific downsides. But in practice most Black players, especially on amateur level, have one favorite system and try to make it work against all the three 6th moves.
There's an irony with 6.Be3 c5 though: Even though it's objectively strong, with Black I would be tempted to avoid it because if White accepts the gambit and knows what he's doing, the queens come off early and things can end up quite drawish. So actually the traditional 6.Be3 with acceptance of the gambit could be a shrewd psychological weapon against King's Indian players out for blood. But that ploy requires a readiness to play in radically different styles from White.