Empty squares (In search of the ephemeral understanding)

Every square that is empty or occupied by a certain piece changes the entire way a position is perceived! In continuation with the previous blog, the following position intrigued me in search for more answers. 

 Here as we saw earlier Black's 51....Rg7+? was a mistake and 51....Rh8! was the only way to draw.  On pondering over why this might be so some surprising ideas in the position seem to surface. Outwardly it might seem that Black might lose a tempo and that is why the move Rg7+ is wrong, but that is not the case as Black is very much within the reach of checking distance by playing his rook to the first rank any time before White gets his pawn to g4. For instance, let us look at the variation given by Jacob Aagard after

51....Rg7+ 52. Kf5 Rf7+ 

this was not played in the game, but is clearly a better defense, and now White should only play only 

53. Kg5!

 if he wants to win the position. If White would play 53. Kg6? it would throw away the win as Black could simply continue 53...Rf8! and it is enough to maintain the equilibrium as White's 54. Ra2 for example would be met by 54.... Ke5! and Black holds as his king is in a strong position to come and attack White's g2 pawn if required by marching himself forward!

and now 54....Rg7+ 55. Kf6 Rg8 56. Ra2!! transposes to a variation from Adams' game which has also been analyzed in detail by Jacob.

So, what does 51...Rh8! do that 51...Rg7+ does not? is a key question to further our understanding of the current position.

 It seems that White's ideal position for his king in these positions is on g5 square where it shoulders his adversary from coming to either f4 or f6. Black should not allow White's king to stabilize on the g5-sqaure, this is why the check on the first move is wrong, as Black cannot shake off White's king from g5 without conceding something in return.

For instance, this position with White's move, White can win as we have seen earlier with Ra2! The placement of the king on g5 gives White the time to shift the Rook via a-file and threaten to come to the g-file via the rank. The analysis of this position has been already dealt with, but it is good to observe the position and understand the importance of the King on g5 in keeping opponent's king at bay.

here Ra2 Ke5 does not save the day for black because of Ra5+ Ke4 Ra4+ and since Black does not have the possibility of king coming to f3, White wins this position by the gain of that one tempo! Compare this with the following position.

Here White's king on g6 is placed worser on g6 than on g5, for example he is not able to get the leverage for Ra2 as it will be answered by Ke5! The critical difference between this and the previous diagram is that Black's king has access to f4 which was not available earlier. Actually, in this position Black does not have to move the Rook at all and can answer White's Kg7 with Rf4 and can just shuttle between d5 and d6 with his king. When White goes back to g5 Black's Rook will start to check again.So essentially even if Black passes White does not have progress here, and Ra2 is always answered with Ke5!

So, in this particular position apart from the basic checking distance principle, shouldering seems to be very important too. Of course, this cannot be seen in isolation and needs to be studied with various principles and variations analyzed in the other two positions.

Link to the previous blog

The full analysis of Nakamura-Lenderman endgame in a repayable Chess base format below

analysis in chessbase format