So far we have a repeat of game 3.

This is the first deviation from game 3. Anand played 15...Bd6 in the third game which led to a wild game where Kramnik misplayed and lost.

The players were moving at a fast pace until this move. Kramnik is taking his time with this next move. He has several options: 17. Bg3 and 17.Bxd6. I like 17.Bg3 better and its idea is to strengthen the g file from the threat of Black's Bishop on b7 and Rook on g8.

Black has a few logical options such as 17...f5, 17...Ke7, 17...Rd8, etc. Black's plan is to create an attack on the Kingside and White's plan is to exploit Black King's position as well as eventually trying to advance his a and b connected passed pawns. 17...f5 seems to be the most aggressive option 

This is one possible wild continuation 18.a4 f4 19.Bh4 Qc5 20.Rfd1 Qh5 21.Kh1 Rxg2 22.Kxg2 Qxh4 23.Bxd7+ Ke7 =+. This is another possibility 18.Rfd1 f4 19.Bh4 Ra5 20.a4 Rxb5 21.axb5 Ne5 -/+. Here is another one 18.Bxd6 Qxd6 19.Rfd1 Ke7 =+ It is obvious why Kramnik is spending a lot of time on this move. This is the critical moment and he could be worse in some of the lines. Frankly speaking, I am very surprised that Kramnik repeated this variation which suits Anand's style a lot better. I am not privy to the preparation from the players but it seems that Kramnik is surprised by 15...Rg8. He is now more than 30 minutes behind on time. Here is another line I just looked at 18.Ne5 Bxe5 19.Qxe5 f6 20.Qe2 Just like other lines above, White has nothing. This is now becoming really curious. Kramnik is now down by more than 50 minutes on the clock.

This is a move I did not anticipate. The most obvious and logical move that came to my head is 18...f4 since that is the reason why Black played 17...f5. Let's examine it 18...f4 19.Bh4 Be7 20.Bxe7 Kxe7 21.Bxd7 Kxd7 and I think it is unclear. I cannot imagine Black playing something else.

This is what I anticipated. White has no way of stopping the eventual exchange of the dark color Bishop which makes the g2 pawn more vulnerable to Anand's attack. Kramnik does have a few options such as 20.Bxe7, 20.Qd3, 20.a4, etc. I like 20.a4 the best. It strengthen the Bishop on b5 to allow the Queen to do other things.

This is now the crucial moment for Anand. Two possible options are 20...Qd6 or 20...Rd8. I personally prefer 20...Qd6 because I would want my Rook to be on the a file for now. If Black tries 20... Bxh4 21. Nxh4 Ke7 22. Qh5 Qd6 and it is also unclear.

It is very difficult to come up with the right plan here given the high stake of the game and how complicated the position is. Their ability to make the right decisions more often than not is one of the reasons why they are World Champions. An interesting try is 22.g3 Rg5 23.Bxd7 Kxd7 24.Nf3 Bxf3 25.Qxf3 Rb8 and White is a little better. Another could be just to get the King out of the g file with 22.Kf1. This game is crucial for both players. If Kramnik falters again, it will be virtually impossible for Kramnik to come back with just 7 games left. On the other hand, if Kramnik wins, it will give him an incredible boost and the momentum will be back on his side. The state of mind of the players could be the most important factor in such a high stake close match such as this. Having been through this myself, I can tell you that it is not fun :)

A complete surprise and an interesting idea. I did not anticipate this move at this juncture. I am not sure if it is the strongest choice. Black has 2 main ideas: To pile the Rooks on the g file with 22...Rg5 or to make a play for the c file with 22...Rac8. Both are playable although I prefer playing for the c file a little more. This is why I do not believe that 22.Ra3 is the most accurate move.