Hi.

About the line:
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Be3 Bg7 5.Qd2 c6 6.Bh6 (D)
Let's have a separate thread. It's a fairly important line. There is more and more practice to go on in many of the continuations as well. Also, previous discussion and analysis on chesspub was done in such a way that it became spread over at least three threads (oops ).



Some previous mentions:
the 4.Bg5 megathread
https://www.chesspub.com/cgi-bin/chess/YaBB.pl?num=1466412326/all
the 4.Bf4 megathread,
https://www.chesspub.com/cgi-bin/chess/YaBB.pl?num=1517943784/all
the 4.Be3 megathread
https://www.chesspub.com/cgi-bin/chess/YaBB.pl?num=1509173142/all

Move orders:
Off the top of my head some move orders would be:
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Be3 Bg7 5.Qd2 c6 6.Bh6
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Bg5 Bg7 5.Qd2 c6 6.Bh6
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Bf4 Bg7 5.Qd2 c6 6.Bh6
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Be3 c6 5.Qd2 Bg7 6.Bh6
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Bf4 c6 5.Qd2 Bg7 6.Bh6
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Bg5 c6 5.Qd2 Bg7 6.Bh6
1.e4 g6 2.d4 Bg7 3.Nc3 d6 4.Be3 Nf6 5.Qd2 c6 6.Bh6 (Modern defense move order)
1.d4 Nf6 2.Bf4 g6 3.Nc3 Bg7 4.e4 d6 5.Qd2 c6 6.Bh6 (London opening move order)

Both 4.Bf4 Bg7 5.Qd2 and 4.Bg5 Bg7 5.Qd2 are quite serious systems and not just 4.Be3 Bg7 5.Qd2. In effect the 6.Bh6 variation has outsized theoretical importance for this reason. If black is happy about playing in a way that allows 6.Bh6 he may well be able to play 4...Bg7 and 5...c6 against 4.Bf4 and 4. Bg5 as well.

Very basic strategic considerations
Playing Bg7 and c6 is very normal for black in general. A standard way of continuing would then be b7-b5. This first of all threatens b5-b4 to annoy the c3 knight, opens a fairly decent development square for the c8 bishop on b7 (sometimes a6) and also in general starts a space grab on the queenside early in case white castles long. If we again take the important position after 4.Be3 Bg7 5.Qd2 c6, White can go 6.a4 to prevent any b5 for what should be a long time. This maximalistic style doesn't have universal appeal though and white has oftentimes sought success with a couple of other moves. Namely 6.Nf3, 6.f3 or 6.h3. These moves are in some sense quite interesting and at least practically threatening. They are not moves that really prevent a 6...b5 move though. I'd say perhaps the key point of 6.Bh6 is that it kinda does. That is because 6...Bxh6 7.Qxh6 b5?! 8.e5! seems quite strong. I've mentioned the aggressive bishop strike as being basically the main move to quite a few people (even titled players) over the years and what has tended to happen next is they tell me "Oh. Is that so. Interesting". The potency and potential of the move is not obvious to all at first sight.

Theory:
Black can either take with 6...Bxh6 or go 6...0-0. Castling at this point is somewhat extra risky though since white can go 7.h4 (See Jones' Coffeehouse repertoire vol. 2 p.376 or Shaw's Playing 1.e4 p.530). I will just refer to those sources on the matter. If black wants to castle short he is probably better off going 4...Bg7 and 5...0-0 without including c6 until move six or not at all. This has been recommended in Dangerous Weapons: The Pirc & Modern

Let's first see what happens if black just goes 7...b5.
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Be3 Bg7 5.Qd2 c6 6.Bh6 Bxh6 7.Qxh6 b5?! 8.e5 dxe5
8...b4 9.Nce2 Nd5 10.Nf3 (+/-)
9.dxe5 Nd5
9...Ng4 10.Qg7 Rf8 11.h3 (+-) Gives black insurmountable problems
9...b4?! 10.Nce2 Nd5 11.Nf3 Bg4 12.Qg7 Rf8 13.Ned4 (+/-) White's position makes a lot more sense
10.0-0-0
10.Qg7!? Rf8 11.O-O-O Qa5 12.Nxd5 cxd5 13.Rxd5 Nd7!?
13...a6 14.Nf3 Qxa2 15.Rd8+ Kxd8 16.Qxf8+ Kd7 17.Bxb5+ axb5 18.Rd1+ Kc7 19.Qd8+ Kb7 20.Qxe7+ Nd7 21.Rxd7+ Bxd7 22.Qxd7+ Kb6 is something white can play, but it looks like he will need very good technique to put pressure on black.
14.a3 Bb7 15.Rd4 Rc8 16.Nf3 Nc5!? 17.Rb4 a6 18.Ng5!? Nb3+ 19.Kb1 Nd2+ 20.Kc1 Nb3+ 21.Kd1 Qc7 22.Bd3 Nc5 Just seems unclear.
10...Qa5!?
10...Be6 11.Bxb5! cxb5 12.Qd2 b4 13.Nxd5 Nc6 14.Nf4 Bf5 15.Qxd8+ Rxd8 16.Rxd8+!? Kxd8 17.Nf3 Bg4 18.Re1 Bxf3 19.gxf3 Should be some suffering for black. White had many other ways of playing as well.
11.Nxd5 cxd5 12.Rxd5 Qxa2 13.Qg7! Rf8 14.Rd8+! Kxd8 15.Qxf8+ Kd7 16.Bxb5+ Nc6 17.Bxc6+ Kxc6(+=) to (+/-) It's a weird position. Black is somewhat active and can struggle on. He should be quite a bit worse though.

The most popular continuation both in correspondence and otb has been taking and going 7...Qa5:
1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Be3 Bg7 5.Qd2 c6 6.Bh6 Bxh6 7.Qxh6 Qa5!?
In order to gain some time from threatening e4 and somewhat preparing b7-b5 again.
8.Bd3!
8.f3 b5 is a lot better for black than after 8.Bd3. Largely due to white not being able to play Nf3. White's strategy should be to hit black before he is ready, so even though it looks mostly like an inconvenience not to be able to play Nf3 it is quite important not to have this move available. After the critical 8.Bd3 we have a few options for black.
8...c5!?
8...b5?! 9.Nf3 Bg4 10.Nd2
Sees white being just better positionally. If Qa5 achieves nothing concrete or has at least some useful function (unlike here), then it actually not that good of a square for the queen.

8...Nbd7
looks a little bit mistimed, but is playable. The basic problem is black needs some kind of idea of how to play after
9.Nf3
and just going
9...e5
Is perhaps not the best. Both 10.0-0 and 10.0-0-0 look quite pleasant for white. There is no real way for black to get white to release the tension. Black doing it himself with exd4 is also probably a bit nice to white. It's worth noting that if the knight was not on d7 black could go Bg4, but now it's tough even to know how to keep developing effectively.

A recent development is...
8...Na6!?
Simply intending to go Nb4 and Nxd3, not worrying about anything else. It's not clear to me if white should go 9.Nf3, 9.Nge2 or even 9.h3!? Nb4 10.Nf3. White has done reasonably well in correspondence practice with 9.Nge2; although there are not a great many recent games with high rated players. I expect more developments in the months and years to come. I will mention that a big part of the reason for not putting the knight on its most natural square immediately would be that the following weird line seems to exist:
9.Nf3!?/?! Bg4 10.Ng5!?
Reasoning being that if black is allowed to take on f3 he is helped by that and if white retreats with Nd2 it is being a bit to nice to black.
10...Nb4 11.0-0
11.h3 avoids the trickiness and could be a little bit better of an attempt for this reason.
11...Nxd3 12.cxd3 Ng8! 13.Qg7 Qxg5 14.Qxh8 Bf3 15.g3 Qh6 16.Qxg8+ Kd7 17.Qxf7
17.Qxa8 Qh3 18.Qxb7+ Kd8 19.Qb8+ Kd7 20.Qb7+ Kd8 21.Qb8+ Kd7 22.Qb7+ (=) Is just a draw by perpetual check.
17...Rf8 18.Qxf8 Qxf8 (D)
It is hard to say who's better or why but I think most people would be ok with playing black here.



9.d5!?
9.Nf3 was suggested by GM Mihail Marin in his "Grandmaster Repertoire The Pirc Defence" (see p.202) and I have to say the move is growing on me. It seems tough to play black. The main idea is 9..cxd4 10. Nxd4 Nc6 11.Bb5! and white will be able to develop more naturally than black in the play to come basically. I would probably even go so far as to go 10...a6 to prevent this bishop move entirely, but then 11.O-O-O!? Nc6 12.Bc4 seems like a decent alternate setup. I think black should even try to simplify to some kind of Sicilian Dragon like late middlegame with 12...Nxd4 13.Rxd4 Be6 14.Nd5 Bxd5 15.exd5, however this is a bit prospect-less.
9...Nbd7
Black basically needs to play this before he tries to get active; which is gonna need to happen at some point. White has more space and an active queen, so something needs to happen.
10.0-0-0!?
This move move looks shocking, but has by now been established. White scores heavily. If I recall correctly I previously described this as a move that just says to black play 10...b5 please. Let me take the pawn and compensation will be insufficient. Black does of course get some compensation however. There has been recent practice.

I should mention as well that there is a major alternative way of playing in
10.Nf3 c4
That looked for a time, before 10.0-0-0, as the big battleground. The whole line saw play in both correspondence and especially otb; in the latter case I would argue because
11.Bxc4 Qc5 12.Bd3 Qxf2+
Is such an appealing move to play
13.Kxf2 Ng4+ 14.Ke2!? Nxh6
And some similar positions were seen and at least for a while white had limited success in correspondence. Now though there can be found a limited number of recent successes

[Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
[PlyCount "135"]

1. e4 d6 2. d4 Nf6 3. Nc3 g6 4. Be3 Bg7 5. Qd2 c6 6. Bh6 Bxh6 7. Qxh6 Qa5 8.
Bd3 c5 9. d5 Nbd7 10. Nf3 c4 11. Bxc4 Qc5 12. Bd3 (12. b3 Qxf2+ 13. Kxf2 Ng4+
14. Ke2 Nxh6 15. a4 Ng4 16. a5 Nge5 17. a6 O-O 18. axb7 Bxb7 19. Nxe5 Nxe5 20.
Ba6 Rfb8 21. Kd2 Kg7 22. Be2 Rc8 23. Ra4 Rc5 24. Nb5 a6 25. Nd4 Rc7 26. Rha1
Nd7 27. b4 Rb8 28. c3 Nf6 29. Bd3 Rbc8 30. Rc1 h6 31. c4 Nd7 32. Ra5 Kf6 33. g4
Ke5 34. Nb3 e6 35. Rf1 Nf6 36. dxe6+ Kxe6 37. Nd4+ Ke7 38. e5 Nxg4 39. exd6+
Kxd6 40. c5+ Ke7 41. Bxa6 Nxh2 42. Re1+ Kf8 43. Kc3 Bxa6 44. Rxa6 Rd7 45. Re4
h5 46. c6 Ng4 47. b5 Nf6 48. Re2 Nd5+ 49. Kc4 Ne7 50. Rea2 Kg7 51. Ra7 Rxd4+
52. Kxd4 Nxc6+ 53. bxc6 Rxc6 54. Rf2 Rd6+ 55. Ke5 {1-0 (55) Reppert,V (1981)
-Hlavica,B (2083) LSS 2020}) 12... Qxf2+ 13. Kxf2 Ng4+ 14. Ke2 Nxh6 15. h3 O-O
16. Kd2 a6 (16... Kg7 17. Rhe1 Rd8 18. b3 Ng8 19. a4 Nc5 20. a5 Bd7 21. Bc4
Rab8 22. a6 b5 23. b4 Na4 24. Nxa4 bxc4 25. Reb1 e5 26. dxe6 fxe6 27. Nc3 Rb6
28. b5 Nf6 29. Nd4 e5 30. Nc6 Bxc6 31. bxc6 Rxc6 32. Rb7+ Rd7 33. Ke2 Rcc7 34.
Rab1 Kh6 35. Rxc7 Rxc7 36. Rb7 Rc5 37. Rxa7 d5 38. exd5 Nxd5 39. Ne4 Ra5 40. g4
Ra3 41. g5+ {1-0 (41) Asquith,J (2399)-Gardner,A (2255) ICCF 2020}) 17. b4 f6
18. Na4 Nf7 19. c4 a5 20. a3 b6 21. Nd4 Bb7 22. Rhb1 axb4 23. axb4 Rfc8 24. Be2
Nfe5 25. Kc3 Kf7 26. Kb3 h5 27. Ra2 Ba6 28. Nc6 Nxc4 29. Nc3 b5 30. Rba1 Bb7
31. Rxa8 Bxa8 32. Nxb5 Ncb6 33. Nba7 Re8 34. Ra5 Rh8 35. Bf3 f5 36. exf5 gxf5
37. Nb5 Kf6 38. Ra7 h4 39. Nc7 Rg8 40. Kc3 Rf8 41. Kd4 Rh8 42. b5 Rf8 43. Bh5
Rc8 44. Be8 Bxc6 45. dxc6 e5+ 46. Ke3 Nc5 47. Bf7 f4+ 48. Ke2 e4 49. Nd5+ Nxd5
50. Bxd5 Ke5 51. Ba2 d5 52. Rh7 Kd4 53. Rh5 Na4 54. Rxd5+ Kc3 55. Rf5 Kd4 56.
Rd5+ Kc3 57. Ke1 Nb6 58. Rd1 Rc7 59. Be6 Rg7 60. Bg4 Kb4 61. Rd7 Nxd7 62. Bxd7
Kc5 63. c7 Rg8 64. Kf2 Ra8 65. c8=Q+ Rxc8 66. Bxc8 Kxb5 67. Bb7 f3 68. g4 {
1-0 (68) Sutton,A (2235)-Gardner,A (2273) ICCF

Continued in next post