1. d4 d5 2. c4 e6 3. Bf4 This move gets the bishop outside the pawn structure. White can't play e4 for a while, and e3 would have shut the bishop in. Moving the bishop out now means that both bishops can be active
Bd6 Not a good idea. Per the following moves the bishop can be exchanged and when the queen takes back she can be pushed back by the c pawn. c6 c5 or Nf6 is normal instead
4. Bxd6 Qxd6 5. c5 Notice that the black queen can't go to a good spot from her current position. If a6 she can be attacked by the light bishop by moving e3 or e4. On c6 she would be ugly, she can only really mov ebackward from there, a4 would rob her of any forward movement and she is lined up with her king on the light squares. On f4 she threatens nothing and can be kicked off at any time by e3.
Qd8 Expected Qe7 threatening to play e5 attacking the base of whites pawn centre
6. Nf3 This move does three things. It makes e5 pointless for now, supports whites pawn chain and takes h4 and g5 away from the black queen. If b4 had been played instead to try and gain space black can mess up whites pawn structure with moves like e5 or a5
Nf6 e4 is a half-hole for black to put his knight on, he could only be kicked off if white moves the f-pawn ( which would mean moving whites knight and ideally castling first ) or by a minor piece trade. The same can be said of e5 for whites knight.
7. b4 Now that d4 is stable ( so c5 is stable ) white can play b4 with the idea of b5 if black plays a5. This would really cramp up the queenside
O-O 8. g3 I think Nc3 would have been better here, leaving more options for where to place whites light square bishop: g3 is pretty commital, and makes playing e3 brittle as whitets pawns are almost all on dark squares making whites light squares pretty weak ( i.e. it would allow black to place pieces safely on light squares within whites camp )
b6 Note that black is just trying to develop here, bxc5 is not threatened as black would then have useless a and c pawns on the queenside. Also white would wreck his own pawn structure playing cxb6
9. Bg2 Placing the bishop where it was committed to and preparing castling
Bb7 10. O-O Nc6 The knight really can't develop to here per text. The knight had to go to d7
11. b5 Pushing the knight away, and then...
Ne7 12. c6 completely dominating the bishop. since e6-e5 can't be played any time soon that diagonal is closed, and the spot on a6 requires b5 to be dealt with
Bc8 13. Nc3 This is neccessary because now the queen protects the rook so white can play a4 and then a4 xb5 if black ever threatens b5
a6 14. a4 As above this will keep the queenside pawns locked down and blacks light bishop immobile
axb5 15. axb5 Rxa1 This is almost forced, the alternatives for blacks rook are to become useless at b8 or to go to a5 where white can trade it off and black has weak pawns on the a & c files and a bishop still locked down
16. Qxa1 Ng6 side by side knights can be a useful setup, look at the fourth rank, they have erected a 4 square barrier. This pattern can be particularly useful in the endgame where the knights can block the king and force him to move half way across the board to get around.
17. Qb2 White now wants to attack blacks weak c7 pawn or infiltrate blacks back rank. While the queen could attempt this it would take a while for here friend the rook to get up to help her. In the meantime blacks queen could counterattack the hanging knight on c3. for example Qa8 Qe7 Ra1 Qb4. Instead the queen will protect the knight from b2, and allow the rook to go up the a-file first.
Qe7 Remember back on move 5 when we said we expected the queen to go to e7 so she can support e6-e5. She now has to take a turn to do so
18. Ra1 Black is threatening e5, so shouldn't I be dealing with that instead of continuing with the infiltration plan? In fact if you look at the position closely e5 loses a pawn per text. Let's see why. d5 would be supported by only one piece and is attacked by two ( if the knight on f3 gets out of the way ) . e5 would be supported by two pieces and attacked by three if the knight on c3 gets out of the way. At some stage N ( c3 ) xd5 would attack blacks queen gaining a tempo
e5 Re8 first makes life interesting white would probably then play Ne5 since NxN pxN would kick off blacks knight at f6
19. dxe5 The tactics here are pretty sticky but essentially a pawn is won
Nxe5 Hopefully obvious that it can't be Qxe5. d4 also fails as follows: d4 exf6 dxc3 fxe7 cxb2 exf8=Q+ KxQ Rb1 and black is down a rook
20. Nxd5 This is the move that really wins the pawn, but it is complicated. If Nxd5 then Nxd5 Nf6 and white is a pawn up. If the queen moves anywhere then Nxf6+ followed by Q or N xe5 puts white up a knight
Nxf3+ The only alternative
21. Bxf3 Now the knight on d5 is supported so the pawn will be held
Nxd5 This is almost forced. If the queen moves away she must move to somewhere where she protects the knight on f6 otherwise NxN PxN opens up blacks king to attack. The only place that satisfies this is Qd8, but then white would still play NxN and the quens would be traded off leading to a pawn upendgame for white and blacks pawns useless
22. Bxd5 Be6
23. Qe5 White could support his bishop with with Rd1 and e4 but the trade would leave white with a backwards ( weak ) pawn on b5 & d5 and ties up whites pieces in defence. White could trade bishops immediately but then the white queen has few options but to stay on b2 protecting e2 and b5 so this move Qe5 pins the bishop to blacks queen, whites bishop can stay on the board where it is perfect for defending b5 and e2
Qf6 Offers the queen trade wreking blacks kingside pawns making whites 4 connected kingside pawns very strong
24. Qxf6 gxf6
25. Be4 preparing to protect e2 and b5
Bc4 26. Bd3 Be6 even if black had traded here black could only win the isolated pawn on d3 by losing the c7 and b6 pawns
27. Kg2 Time to get the king busy
f5 28. Ra7 This could have been played at any stage to lock blacks rook down in defence of the pawn. The pawn cannot be protected by the bishop.
Rc8 29. Kf3 Aim at the f5 pawn
Kg7 30. Kf4 Kf6 31. Now black loses a piece with any move other than his h-pawn
h3 h6 32. f3 White has more waiting moves than black so can wait him out. White should do so in a way that keeps his pawn intact.
Bb3 33. Bxf5 The pawn is won and comlete disaster is threatened on the c8 and c7 squares
Be6 Essentially forced
34. Bxe6 fxe6 35. e4 This move makes a spot for whites rook on d5 where it can block the d-file and protect b5
e5+ 36. Ke3 Ke6 37. Ra2 If black attempts Rd8 then white can play Rd2, if not then white will play Rd2 and then Rd5 anyway
Kd6 38. Rd2+ Ke6 39. g4 Now Rd5 and Rd7 are always options, so they don't need to be played right away
Rf8 40. Kf2 The king will now help to push the g and h pawns
Kf6 41. Kg3 Ke6 42. h4 Re8 43. Rd7 Now that the g and h pawns are close enough to promotion the rooks can be traded off
Re7 44. Rxe7+ Kxe7 45. g5 Blacks king cannot take both the b and g pawns so is lost
h5 46. f4 exf4+ 47. Kxf4 Ke6 48. e5 Kf7 49. Kf5 1-0