Ulhumbrus: The minister of defence becomes the minister for war this time and outplays Shankland.The computer evaluations and analysis suggest that Shankland's main mistake is to play the pawn advance ...a3 at the wrong moment, more specifically, to over prepare it and so delay it for too long.
Instead of playing it at move 26 the right moment to play it is five moves earlier at move 21.
After 21..a3! Black is able to open the a file before White is able to open the g file.
One point of this is that if the opening of the a file is accompanied by a threat, it comes then with tempo, or with gain of time: It gives White no time to continue his proceedings on the king side but compels him to drop what he is doing there. More on this later.
Instead of 21...a3 Black delays this attack for five moves. According to Lasker a great deal can happen in five moves: Five moves in chess is a long time
What does happen during these five moves is that Karjakin exchanges the black squared bishops and removes all of the remaining obstructions to his rook on the g file after which he is ready to start a winning king side mating attack
After 26...a3 it is too late for Shankland to open the a file and 27 Rxg7+! starts a winning mating attack. On 27...Kxg7 at least one commentator ( GM Short) as well as the computer gave the move 28 Ng4!! This is the first of a pair of moves, a pair of which the second move is Qh6+, and Black has no satisfactory answer to this threat. Moreover after that ( as Short indicated as well, amongst other things) the N may go to f6 to support further the attack of the queen on h6.
This suggests that the move Ng4 counts as a potential winning king side attacking threat. Moreover the evaluation of the attack may depend on whether White has a resource like this. Without it Black's queen side attack may get in first instead.
One point brought out by the right moment for the queen side attack ...a3 is that it not only threatens to break through or win material there but distracts White from his king side attack.
Thus on 21...a3! suppose that White proceeds as in the game. On 22 g5 axb2 White has no time to continue his king side attack but has to delay it. On 23 Rab1( the first delay) 23...hxg5 24 Bxg5
24...Bxg5 25 Nxg5 Ra1 White has no time to play Bf1. On 26 Rxa1 ( the second delay ) 26...bxa1 ( Q) 27 Rxa1 Nxd4! the white queen is overloaded: If she has to defend her knight she cannot also defend the d pawn.
At the risk of repetition Shankland's main mistake was to delay the queen side attack ...a3 for too long. When he did play it, it was too late: Karjakin was ready to start his mating attack.
One example of an explanation is that Shankland saw too late some attacking resource on the part of Karjakin after having made some earlier choice.
Kibitzing
sac: 27.Rxg7+
icon.
