Here are the moves, with analysis.
1. e4 e5 {Bye-bye Caro Kann Defense for now. Although Carlsen used it very successfully in the second game of the match he did not find a point in repeating the same opening. This reveals a certain strategy on the part of Carlsen. With white so far, he is sticking to his guns while with black he wants to keep Anand guessing.}
- Anand battles from lost position to draw fourth game
2. Nf3 Nc6 3. Bb5 {The Ruy Lopez has been Anand's pet for a very long time. He has won some big games in this.}
3. Nf6 {The Berlin defense was made popular by Vladimir Kramnik of Russia who used it successfully in his match against compatriot Garry Kasparov in 2000 Braingames World Championship match at London.}
4. O-O {Anand goes for the most principled system. The 'Berlin wall' as it is called, typically reaches a queen-less middle game in the early phase. White gets better pawn structure against double Bishops.} Nxe4
5. d4 Nd6
6. Bxc6 dxc6
7. dxe5 Nf5
8. Qxd8+ Kxd8
9. h3 {All this is standard theory and has been played at elite levels many times.} Bd7
10. Rd1 Be7 {The big surprise by Carlsen. This move has been played four times previously and three times out of those by Carlsen's friend and second Jon Ludvig Hammer. In fact, Anand's second in the last three world championship campaign - Surya Shekhar Ganguly defeated Hammer in the war of the seconds in 2011 in this variation.}
11. Nc3 Kc8
12. Bg5 {Principled as white wants to trade this Bishop. Black does not have a pair of Bishops anymore so technically he should be worse. However, black has no weaknesses and this is what prompts Carlsen to allow this exchange.} h6
13. Bxe7 Nxe7
14. Rd2 c5
15. Rad1 Be6 {Both the players are playing with a certain plan in mind. Black's next aim would be to connect the rooks.}
16. Ne1 Ng6
17. Nd3 b6
18. Ne2 {An inaccuracy according to the chess engines but Anand was probably looking to seize the initiative.} Bxa2 {This move shows Carlsen's confidence, precise calculation and remarkable intuition. Not many would have given this a second thought while others would just say it will make the position passive.}
19. b3 c4
20. Ndc1 cxb3
21. cxb3 Bb1
22. f4 Kb7
23. Nc3 Bf5
24. g4 Bc8 {After a big our on many squares, the Bishop is back from where it started. Carlsen must have expected this position while taking the pawn.}
25. Nd3 h5
26. f5 Ne7.
27. Nb5 {Anand realises that the position is now slipping out of hands and makes his bid for a counter play} hxg4
28. hxg4 Rh4 {Precise like a machine, the Norwegian continues to pose more problems for Anand.}
29. Nf2 Nc6
30. Rc2 a5 { Now its time to take measures to activate the other rook.}
31. Rc4 g6 {Another correct move that keeps the balance in black's favour.}
32. Rdc1 Bd7
33. e6 {This is the only move. White is much worse but Anand keeps finding the right moves to create problems in Carlsen's quest for a win.} fxe6
34. fxe6 Be8
35. Ne4 {A nice manoeuvre found in time pressure. Anand see no point in playing passively and goes for some activity.} Rxg4+
36. Kf2 Rf4+ {Probably not so precise as Nc5 was not a great threat yet. Black could have played Rd8 instead.}
37. Ke3 Rf8 {The only move that works.}
38. Nd4 Nxd4
39. Rxc7+ Ka6
40. Kxd4 {Anand recovers one of the lost pawns, now has a rook on seventh and a pawn on the sixth. Carlsen was not at all pleased with himself at this point.} Rd8+
41. Kc3 {Perhaps not the most precise as Ke3 would have kept the balance anyway. However, Anand seeks a theoretically drawn endgame from this point.} Rf3+
42. Kb2 Re3,
43. Rc8 {The move Anand had planned.} Rdd3 {Carlsen continues to come with moves to keep the game alive. This is one ability that has made the world number one what he is today.}
44. Ra8+ Kb7
45. Rxe8 Rxe4 {The players now reach a rook and pawns endgame that should be drawn.}
46. e7 Rg3
47. Rc3 Re2+
48. Rc2 Ree3 {Again, Carlsen wants to play on.}
49. Ka2 g5
50. Rd2 Re5
51. Rd7+ Kc6
52. Red8 {Precision by Anand. He simply doesn't let go. One correct move after another.} Rge3
53. Rd6+ Kb7
54. R8d7+ Ka6
55. Rd5 {Now the outcome is no longer in doubt. The longest game of the match so far also finally sees the same result as the first three.} Re2+
56. Ka3 Re6
57. Rd8 g4
58. Rg5 Rxe7
59. Ra8+ Kb7
60. Rag8 a4
61. Rxg4 axb3
62. R8g7 Ka6
63. Rxe7 Rxe7
64. Kxb3 {Black's extra pawn is inconsequential. Draw.}
1/2-1/2.
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