Critical position with the pawn on a4

D. 1



As we have seen (thread „Carlsen – So (2021)”), with Black to play this ending should be a draw with correct play. White to play the position is won. White has 2 winning moves - 1.Ra7 and 1.a5. 
 
1.Ra7

1.a5 transposes after 1...Ra1+ 2.Kf2! Kh7 3.Ra7! Kh6 4.a6 into main line. 
a7 is an optimal square for the white rook because it impedes the g7-g5 advance after 1...Kh7 2.a5!  If White plays 1.Ra8+?, then after 1...Kh7 2.a5 Black can immediately play 2...g5 or do it after 2...Ra1+ 3.Kh2 (see D. 1-1).

1...Kh7 2.a5! Kh6 3.a6

Or 3.Ra8 which has been analysed in Carlsen-So, D. 3, line 1...Kh7 2.a5 Kh6? 3.Ra8. 

D. 2



This position is won also with the position of the white king on h2, h3, g3.  Black cannot prevent the white king from advancing to the centre.

3...Ra1+ 

After 3...g5 4.hxg5+ fxg5 5.Ra8! Kg7 6.a7 Ra1+ 7.Kf2! the king walks to the center and attacks the e5 weakness.   

4.Kf2! 

The king must not allow himself to be imprisoned. 4.Kh2? throws away the win. 4...g5! 5.Kg3 Ra3! (see the analyses in Carlsen-So, D. 3-1, after 4…Ra3! 5.Ra7 Kh6! 6.a6 g5!). 

4...Ra2+ 

4...g5 5.hxg5+! Kxg5 (5...fxg5 6.Ra8! h4 7.a7 Kg7 8.Ke2+–) 6.Ra8 Ra2+ 7.Kg1 Kf4 8.a7 Ke3 9.Rf8 Rxa7 10.Rxf6+–.

5.Kg3!

D. 3



5...g5

This move (unlike D. 3-1, after 4…Ra3! 5.Ra7 Kh6! 6.a6 g5!), does not save, because without pinning the white king from а3 the g5-g4 advance is useless.    
5...g6 6.Ra8 f5 7.a7 is also does not help.   

6.Ra8!

D. 4



6...Kh7

6...Kg7 7.a7! Ra1 8.hxg5! fxg5 9.Kf2!+–.

7.a7 Kg7


D. 5



8.Kh2! Ra1
 
8...gxh4 9.Kh3! Ra1 10.Kxh4 Rh1+ 11.Kg3 Ra1 12.Kh2 Kh7 13.g3+– (13.g4+–). 

D. 6 after 8...Ra1



9.g4! hxg4

9...gxh4 10.gxh5! Ra3 11.Kh3+–; 9...Ra2+ 10.Kg3! hxg4 11.hxg5! fxg5 12.Kxg4!+–. 

10.hxg5! fxg5

10...gxf3 11.gxf6+!+–. 

11.fxg4!+–.

Back to the initial position in D. 1

D. 1-1



1.Ra8+? Kh7!

1...Kf7? 2.a5!+–.

2.a5 g5 

Or 2...Ra1+ 3.Kh2 g6 (3...g5 4.hxg5 fxg5! 5.a6 Kg7 6.a7 Kh7! 7.Kg3 Ra2!=) 4.a6 f5 5.a7 f4 6.g3 fxg3+ 7.Kg2 Ra2+ 8.Kxg3 Kg7 9.Re8 Rxa7 10.Rxe5 Ra1=. 

Immediately 2...g6? without 2...Ra1+ loses, because without this check White manages to go the queenside after 4...f4 5.Kf1! 3.a6! f5 4.a7 f4 5.Kf1!+–. 

3.hxg5 fxg5 4.a6 Ra1+! 5.Kf2 Ra2+! 6.Kg3 Kg7=.