Komodo plays a model Grunfeld against Igel, pushing rook’s pawns AlphaZero-style on both wings to squeeze Black for space then cutting through Black’s porous kingside dark squares with a fine exchange sacrifice.
Any 1.d4 players who face the Grunfeld should note this as a model game: it’s a perfect example of what White should be aiming for!

1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.cxd5 Nxd5 5.e4 Nxc3 6.bxc3 c5

The TCEC opening book ended here. The immediate 6…c5 is much less common than 6…Bg7, but it is ventured occasionally by strong Grunfeld players perhaps to sidestep lines such as 6…Bg7 7.Qa4+ which occasionally enjoys a burst of popularity at the elite level.

7.Bb5+

Another white idea that is periodically wheeled out against 6…Bg7, and it is also interesting against 6…c5.

7…Bd7 8.Bxd7+ Nxd7

An important decision for Black. 8…Nxd7 prioritizes development but abandons the possibility of pressuring d4 with …Nc6 (which would be possible after 8…Qxd7). Both Leela and Stockfish preferred 8…Qxd7 in my engine matches. In all cases however, Black’s difficulties revolve around finding an active role for the queen’s knight and Igel suffered terribly from this in the game.

8…Qxd7 9.Nf3 Bg7 10.0–0 0–0 11.Bf4 (11.Rb1 Nc6 12.d5 Na5 13.Qd3 Qa4 14.Bg5 Rfe8 15.Nd2 h6 16.Be3 b6 17.f4 Rad8 18.f5 e6 19.fxg6 fxg6 20.d6 c4 21.Qe2 e5 22.Qf2 Rf8 23.Qh4 Rxf1+ 24.Nxf1 Rxd6 25.Bxh6 Bxh6 26.Qxh6 Qc2 27.Rc1 Qxe4 28.Ne3 Rd3 29.Re1 Nc6 30.Nc2 Qg4 31.Rf1 Rd8 32.h3 Qh5 with a balanced position ½–½ (64) Leela-Stockfish Matthew Engine Games 2021) 11…Nc6 12.d5 Na5 13.Ne5 Qd6 14.Nd3 Qa6 15.h4 Rac8 16.Rc1 Nc4 17.Re1 e5 18.Bh2 Rfe8 19.h5 Qxa2 20.Ra1 Qd2 21.Qxd2 Nxd2 22.Rxa7 c4 23.Nb4 Ra8 24.Rxa8 Rxa8 25.h6 Bf8 26.Bxe5 Re8 27.d6 Rxe5 28.d7 Be7 29.Ra1 f6 30.Ra8+ Kf7 31.Nd5 Ke6 32.Rh8 Nxe4 33.Nxe7 Kxd7 34.Ng8 Nxc3 35.Rxh7+ Kc6 36.Ne7+ Kb6 37.Nxg6 Rc5 38.Nf4 Nd5 39.Ne6 Rc8 40.Rd7 Nb4 41.Rd4 Nd3 42.Rh4 Rh8 43.h7 Kc6 44.Nd4+ Kd5 45.Kf1 Ne5 ½–½ (71) Stockfish-Leela Matthew Engine Games 2021. The game eventually ended in a draw but Black was right on the edge for many moves!

9.Nf3 Bg7 10.h4

The march of the rook’s pawn is a well-known theme in modern human chess, influenced by the example of AlphaZero. Magnus Carlsen in particular has made copious use of this theme in Grunfeld structures. 10.h4 is however a novelty in this exact position. The advance of the rook’s pawn is a low-cost opening salvo in a potential attack on the kingside. Black has a typical dilemma to resolve: halt the rook’s pawn right away with …h5 (weakening g5), half-block with …h6 (when Black’s h-pawn moves to a square attacked by White’s dark-squared bishop) or allow the white h-pawn to advance to h5 (putting pressure on the black kingside) or even to h6 (AlphaZero-style) restricting the black king and fixing the h7–pawn as an endgame weakness. Igel opts for the balanced option, playing …h6, ready to meet h5 with …g5.

10…Qa5 11.Bd2 h6 12.a4

Another rook’s pawn destined to exert significant influence on the game. To start with, the a-pawn restricts black queenside expansion with …b5 as well as the typical activation of the black knight to a4 via b6.

12…0–0 13.0–0 e6 14.Qe2 Rfc8 15.Rfe1

It’s intriguing that Stockfish and Leela find clear – and far from obvious – paths to holdable endgames from this position. It’s an illustration of how much better they are than other engines and why it’s so interesting to also run matches with other engines.  You need to know what happens without perfect play!

15…Qc7

15…Qa6

was an unexpected choice from Leela but turned out beautifully in my engine games. The exchange of queens is achieved so early that White lacks time to consolidate its position before Black’s counterplay arrives. It’s on the edge though: if Black’s counterplay fails to land, White will essentially be a pawn up due to Black’s wrecked queenside pawns. Leela scored 2/2 draws with this idea in my games! 16.Qxa6 bxa6 17.Reb1 a5 Fixing the pawn on a4 for attack by a knight on b6 18.g3 Rab8 19.Rb5 cxd4 20.cxd4 Nc5 A great tactical idea exploiting the pin along the h8–a1 diagonal. 21.e5 Rxb5 22.axb5 Nb3 23.Ra4 Rb8 24.Bxa5 Rxb5 25.Be1 Rb7 26.Bb4 Bf8 27.Bd6 Bxd6 28.exd6 f6 ½–½ (51) Stockfish-Leela Matthew Engine Games 2021

16.a5

Tying down the black queenside, and taking away the b6–square from Black’s knight. The importance of this becomes clear after White’s 18th move.

16…a6

i) 16…b6 17.a6 doesn’t allow the knight on d7 to free itself, so Black fixes the a-pawn on a5 and prepares …b6 to give the knight on d7 some scope.;

ii) 16…cxd4 17.cxd4 Nf6

The knight accesses f6 before White plays e5 to prevent it. Now after e5, Black can occupy the outpost on d5.

18.g3 Qc4 19.Rab1 Qxe2 20.Rxe2 b6 21.axb6 axb6 22.Rxb6 Rc2

A pawn sacrifice I’ve seen Stockfish make many times now in this pawn structure (I’ve also seen it many times in the Semi-Tarrasch: 1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.Nc3 c5 5.cd Nd5 6.e4 Nxc3 7.bc cd 8.cd). The activity of Black’s rook on the 7th, the weakness of the e4–pawn, some unexpected counterplay with …g5 and some precise calculation keeps the game well within the drawing zone!

23.Rb1 g5 24.hxg5 hxg5 25.e5 (25.Nxg5 Bh6 26.Nf3 Raa2 27.Rd1 Bxd2 28.Rdxd2 Rxd2 29.Nxd2 Nxe4 30.Rxe4 Rxd2 is a drawn rook and pawn endgame.) 25…Nd5 26.Re4 Ra3 27.Rb8+ Bf8 28.Be3 Nxe3 29.Rxe3 Raa2 30.d5 g4 31.Ne1 Rxf2 32.d6 Rfd2 33.Rd3 Re2 34.Rd1 Kg7 35.Rc8 Rxe5 36.d7 Be7 37.d8Q Bxd8 38.Rcxd8 Re3

Stockfish adopts the common engine defensive stratagem – explained in “The Silicon Road to Chess Improvement” in the chapter on Engine Sacrifices – of heading for a pawns vs knight ending. It proves enough here too!: ½–½ (62) Leela-Stockfish Matthew Engine Games 2021

17.Reb1 Rcb8

17…b6 18.axb6 Nxb6 19.Rxa6 wins a pawn.

18.e5

Another move typical of AlphaZero, and once again a stratagem used frequently by Magnus Carlsen in the Grunfeld. The d4–e5 structure blocks out the bishop on g7, creates an outpost for a white knight on d6 and fixes dark square weaknesses in Black’s camp (for example f6). The drawback is normally the excellent outpost on d5 conceded to a black knight, but here the a5–pawn bars the knight’s natural path to d5 via b6.

18…b5

18…b6 seemed more logical to me, forcing the removal of the a5–pawn and thus freeing Black’s knight to reach c4 and d5 via b6. There are some tactical problems however… 19.h5 (19.axb6 Rxb6) 19…g5 (19…gxh5 is the best reaction. 20.Rd1 bxa5 21.Ne1 Qb7 22.Rxa5 cxd4 23.cxd4 Nf8 24.Qxh5 Qe4 25.Nf3 Rb5 26.Ra3 a5 27.Kh2 a4 28.Re1 Qg6 29.Qxg6 Nxg6 30.Rea1 f6 31.exf6 Bxf6 32.Rxa4 Rxa4 33.Rxa4 ½–½ (79) Stockfish-Leela Matthew Engine Games 2021. An extra pawn, but not enough for victory!) 20.Nxg5 hxg5 21.Bxg5 f6 22.exf6 Nxf6 23.h6 Bh8 24.axb6 Rxb6 25.Bxf6 Bxf6 26.Qe4

is the nasty point! 26…Rf8 27.Rxb6 Qxb6 28.Rb1 followed by Rb7

19.Re1

A move that looks really odd! Why play the rook to b1 from e1 on move 17 and then move it where it came from 2 moves later? In fact, it’s understandable if you consider that the engines consider Black’s best reply to move its rook on b8 back to c8! In that case, we’ve had a little additional rook shuffle but the end result is the same! White doesn’t capture en passant, leaving the a5–pawn where it is to block …Nb6–d5.

Quite remarkably, White doesn’t anticipate the soon to be opened c-file with 19.Rc1 focusing instead on the kingside, targeting the h6–pawn (a weakness created by 10.h4!) with a queen and bishop battery along the c1–h6 diagonal. In general White always has the option of playing a rook to the c-file later, so the c-file is not permanently conceded. And in fact, the rook on e1 supports tactical possibilities against the black kingside that would not be possible with a rook on c1.

19…Rc8

19…Qb7 20.h5 g5 21.Nxg5 hxg5 22.Bxg5 f6 23.Bf4 Re8 (23…fxe5 24.h6) 24.h6 Bh8 25.Qh5 and it’s crucial that the rook on e1 prevents the black queen from swinging over to defend the kingside with …Qe4!

20.Bf4 cxd4 21.cxd4 Qc3

Preventing Qe3 targeting h6.

21…Qb7 22.Qe3 h5 was Stockfish’s and Leela’s defensive choice at this point, drawing quite a few and losing a couple. That seems to indicate that White already has good chances by targeting the kingside dark squares with manoeuvres such as Bh6 and Nd2–e4–d6/f6. White can also target the f7–pawn with Qf4 followed by transferring a rook to the third (another stratagem that receives a whole chapter in “The Silicon Road to Chess Improvement“)

a) 23.Bh6 Qd5 24.Qf4 Rc3 (24…Rc4 25.Bxg7 Kxg7 26.Rec1 Rf8 27.Rxc4 bxc4 28.Ra3 Nb8 29.g4 hxg4 30.h5 Nd7 31.h6+ Kh8 32.Qxg4 Qb5 33.Rc3 Qb4 34.Rc1 c3 35.Qe4 Qxa5 36.Ng5 Qb4 37.Qe3 Nb6 38.Qxc3 Qe7 39.Qg3 Nd5 40.Rc5 Ra8 41.Ra5 Nc3 42.Kf1 Rf8 43.Rc5 Nd5 44.Kg2 Qd7 45.Kh3 Qd8 46.Rc4 Kg8 47.Rc6 Ne7 48.Rd6 Qc8 49.Qa3 a5 50.Kh2 Qc2 51.h7+ Kg7 52.Kg2 Qf5 53.Qg3 Kh8 54.Rd7 Nd5 55.Kh2 a4 56.Qh4 Nc3 57.Ra7 Nd1 58.f3 Ne3 59.Kg3 a3 60.Rxa3 Nc4 61.Ra7 Ne3 62.Rd7 Nd5 63.Rb7 Ne3 64.Kf2 1–0 (64) Stockfish-Leela Matthew Engine Games 2021) 25.Rac1 b4 26.Rxc3 bxc3 27.Rc1 Qxa5 28.Ng5 Rf8 29.Ne4 c2 30.Nf6+ Bxf6 31.Bxf8 Bxe5 32.dxe5 Kxf8 33.Rxc2 Qe1+ 34.Kh2 Qxe5 35.Qxe5 Nxe5 ½–½ (160) Stockfish-Leela Matthew Engine Games 2021;

b) 23.Rab1 Rab8 24.Bg5 b4 25.Nd2 Bf8 26.Bh6 Rc3 27.Qf4 Rd3 28.Bxf8 Rxf8 29.Ne4 Rxd4 30.Nf6+ Nxf6 31.Qxd4 Nd5 32.Rec1 Kg7 ½–½ (157) Stockfish-Leela Matthew Engine Games 2021. Black held the draw.;

c) 23.Nd2 Qd5 24.Rab1 Nb8 25.Ne4 Nc6 26.Nd6 Nxa5 27.Nxc8 Rxc8 28.Qa3 Qxd4 29.Be3 Qa4 30.Qxa4 bxa4 31.Rb4 Nc6 32.Rc1 Bxe5 33.Rxa4 Ne7 34.Rxc8+ Nxc8 35.Rxa6 Ne7 36.Ra5 Bc3 37.Ra8+ Kg7 38.g3 Bb2 39.Kg2 Nd5 1–0 (149) Stockfish-Leela Matthew Engine Games 2021. Amazed Stockfish managed to win this!;

22.Qe4

The queen is excellently-placed on e4; White is even threatening to win back “Black’s” c-file with Rac1 and Qb7. This theme of invading through the channel the opponent opened is a common one in engine chess and merits a whole chapter in “The Silicon Road to Chess Improvement“!

22…Qc6 23.Qe3

23…Qc3

Black gives up a kingside pawn to nullify White’s attacking chances on that wing, hoping for a breathing space to prosecute its counterplay on the queenside. Black’s problem is getting the knight on d7 involved which it really needs to create serious threats. However, by the same token, White too needs a fresh plan now that a kingside mating attack is off the menu.

i) 23…h5 again led to a mix of wins for White and draws. It’s very similar to 21…Qb7 22.Qe3 h5 except that Black’s queen is somewhat clumsily-placed on c6 rather than b7.

24.Bg5 Bf8 25.Nd2 Qd5 26.Rad1 Bb4 27.Ne4 Bxe1 28.Rxe1 b4 29.Qf4 b3 30.Bh6 f5 31.exf6 Qxa5 32.f7+ Kh8 33.Rb1 Qf5 34.Rxb3 Qxf4 35.Bxf4 Ra7 36.d5

will bring echoes of the game when you see it! 36…exd5 37.Nd6 Rf8 38.Re3 Raa8 39.Re7 Nc5 40.Be5+ Kh7 41.Ne8 a5 42.Nf6+ Kh6 43.Re8 Kg7 44.Nxd5+ Kh6 45.Nf6 Rd8 46.Kh2 Nb7 47.Re7 Nc5 48.Ne8 Kh7 49.Bg7 Rxf7 50.Rxf7 Rxe8 51.Bc3+ Kg8 52.Rg7+ Kf8 53.Rxg6 1–0 (66) Stockfish-Leela Matthew Engine Games 2021;

Black’s best defensive plan was (of course) demonstrated by Stockfish in my engine games:

ii) 23…Kh7 24.h5 gxh5

Once again this reaction to h5 proves correct. Allowing hg ..fg creates a new weakness in Black’s position in the form of the e6–pawn and robs Black of any chance to challenge White’s centre with …f6. (24…Qc3 25.hxg6+ fxg6 26.Qe2 Qc4 27.Qe3 Qc3 28.Rec1 Qxe3 29.Bxe3 g5 30.Ne1 proved surprisingly difficult for Black to hold in my engine games! The White knight comes to d3 and White pushes its kingside pawns, often supported by its king. 30…Bf8 31.Kf1 Rab8 32.Nd3 Kg6 33.g4 Rc4 34.f4 Rbc8 35.Rxc4 bxc4 36.Rc1 Ba3 37.Rc2 Be7 38.Kf2 c3 39.Ke2 Bd8 40.d5 exd5 41.e6 Nf6 42.Ne5+ Kg7 43.f5 h5 44.Bd4 hxg4 45.Nd7 Rc4 46.Kd3 Rxd4+ 47.Kxd4 Bxa5 48.e7 Ne8 49.Rh2 c2 50.Rxc2 g3 51.Kxd5 Kf7 52.f6 Bc7 53.Rc1 Bf4 54.Rh1 Nc7+ 55.Kc6 g2 56.Rg1 1–0 (56) Stockfish-Leela Matthew Engine Games 2021) 25.Nd2 f5 26.exf6 Nxf6 27.Be5 Ng4 28.Qd3+ Kg8 29.Bxg7 Qc2

The final point in an exceptionally clever tactical defense that manages to break White’s central bind and exchange enough pieces to force the game into a drawable double-rook endgame a pawn down. 30.Qxc2 Rxc2 31.Bxh6 Nxh6 32.Rxe6 Rxd2 33.Rxh6 Rxd4 34.Rxh5 Rb8 ½–½ (97) Leela-Stockfish Matthew Engine Games 2021

24.Bxh6 Qxe3 25.Bxe3 Nb8 26.g4

A really good plan from White, ignoring Black’s desperate attempts to mobilize its knight on the queenside and activating its own kingside pawn majority.

26…Nc6 27.h5

The pressure on the kingside is unpleasant for Black. One idea is simply to weaken Black’s structure with hxg6 followed by Ng5 attacking the now isolated e6–pawn. Black should consider …gh, gh at some stage but this opens the g-file against its king and gives White a dangerous passed h-pawn.

27…Nb4 28.Rab1 Nc2 29.Re2 Rab8 30.hxg6 fxg6 31.Ne1 Na3

31…Nxe1 32.Rexe1 b4 33.Rb3 Rb5 34.Ra1 Bf8 35.Kg2 and it’s hard to find much more for Black to do while White brings the king to e4 and activates its kingside majority with f4–f5.

32.Rb3 Bf8

32…Nc4 33.Nd3 aiming for c5 (forking a6 and e6) or f4 (forking e6 and g6) 33…Nxa5 34.Ra3 and White maintains a pawn plus by regaining the a-pawn (after which e6 is under attack).

33.Ng2 Rc6 34.Nh4 Kf7 35.Kg2 Be7 36.Bh6

It wasn’t at all clear to me where this was leading. Komodo has an extraordinary tactical idea in mind.

36…Rg8

36…Bxh4 37.Rxa3

37.Rf3+ Ke8 38.Rf6!!

A fantastic and extremely deep idea, relying on the constriction of the black king, the porous Black’s kingside dark squares and the absence of a defensive black minor piece (look where the black knight is!) Breaking a “fortress” by sacrificing the exchange was also a theme we noticed in AlphaZero’s games, dedicating a section of “Game Changer” to that.

38…Bxf6 39.exf6 Kf7

39…Rh8 40.Nxg6 Rxh6 41.f7+ Kxf7 42.Ne5+ Beautiful tactics!

40.Nf3 Kxf6

40…Rd6 41.Ng5+ Kxf6 42.Ne4+; 40…Rc2 41.Ng5+ Kxf6 42.Rxe6#; 40…Nc4 41.d5 exd5 (41…Rd6 42.Ng5+ Kxf6 43.Ne4+ Ke5 44.f4+ Kxd5 45.Nf6+ Lovely!) 42.Re7+ Kxf6 43.Bg5#

41.Bg5+ Kg7 42.d5

42…exd5

42…Rd6 43.Be7 picks up the loose knight on a3! 43…Rxd5 44.Bxa3 Re8 45.Rc2 e5 46.Ng5 b4 47.Bxb4 Rd4 48.Bd2 Rxg4+ 49.Kh3 Rg1 50.Rc7+ Kg8 51.Ra7 Rd8 52.Be3 1–0 (52) Stockfish-Leela Matthew Engine Games 2021;

42…Rc2 43.Rxe6 with threats both of queening the d-pawn and mating the black king starting with Ne5!

43.Re7+ Kh8 44.Nd4 Rgc8

44…Rd6 45.Ne6 and Bf6 is terrible for Black

45.Ne6

Ignoring the immediate win of the exchange which would give Black a defensive barrier along the 6th rank. Now after 45…Rxe6 46.Rxe6, White’s rook stands perfectly hitting g6 and a6. Meanwhile, Ne6 shields the f6–square which means the black king is now in danger from Bf6+.

45…Kg8 46.Rg7+ Kh8 47.Rxg6 Kh7 48.Rg7+ Kh8 49.Re7 Kg8 50.Bf6

intending g5–g6 followed by mate with Rg7+, Rh7++ and Rh8+mate!

50…R8c7 51.Nxc7 Rxf6 52.Rd7 Nc4 53.Kg3 d4 54.Rxd4 Nxa5 55.Rd8+ Rf8 56.Rd5

Material is level(!) but Black is in serious trouble as its pawns are vulnerable, its king is remote on the back rank and White’s pawns are mobile. Moreover, the black knight must stay around the queenside pawns or they will be lost which means it is not available to help defend the kingside.

56…Rf6 57.f4 Nb7 58.Re5 Rc6 59.Nd5

58.Re5 and 59.Nd5 is beautiful technique from White, securing dominating positions for its pieces which both restrain Black’s queenside pawns and support White’s own advancing pawns.

59…Kf8 60.g5 Nd6 61.Kg4 a5 62.Ne7 Rc7 63.Nf5

Again excellent technique, spotting a small tactic to win one of Black’s queenside pawns

63…Nc4

63…Nxf5 64.Rxf5+ Kg7 65.Rxb5 Ra7 66.f5 a4 67.g6 a3 68.Kg5

68…Ra8 (68…a2 69.f6+ Kg8 70.Rb8#) 69.Rb7+ Kg8 70.f6 a2 71.Rg7+ Kf8 72.Rh7 Kg8 73.f7+ Kf8 74.Rh8+ Ke7 75.Rxa8 and White is just in time! Worth knowing!

64.Rxb5 Kf7 Necessary to stop g6.

64…a4 65.g6 Rc8 66.Rb7 wins

65.Nh6+ Ke6 66.f5+ Kd6 67.g6 Kc6 68.Rb1 Rg7 69.Kh5 Ne5 70.Ng4 Nd3 71.f6 Rg8 72.f7 Nf4+ 73.Kg5 Ne6+ 74.Kf6 Rxg6+ 75.Kxg6 Nf8+ 76.Kf5 Kc7 77.Ra1 Kb6 78.Rxa5 1–0