https://www.youtube.com/watch?v=1Jc0hDxV_Gs
@john2001plus
0 seconds ago
It was obvious to me that this was a classic corresponding-squares problem. Starting from the left, the Black king must be on b6 when the White king is on c4. If the Black king is on a6 then he is too far left to prevent the White king from marching to h5. From this we obtain five more corresponding squares: the White squares d3, e3, f3, g3, and h4 correspond, respectively, to the Black squares c7, d7 e7, f6, and g6. If it is Black's turn when both kings occupy corresponding squares, Black is forced out of position.
I would call this a master level endgame. These corresponding-square problems arise when the king is trying to advance on one of two sides, and the enemy king is trying to guard both sides. So the two kings do a dance to out maneuver the other.
@john2001plus
0 seconds ago
It was obvious to me that this was a classic corresponding-squares problem. Starting from the left, the Black king must be on b6 when the White king is on c4. If the Black king is on a6 then he is too far left to prevent the White king from marching to h5. From this we obtain five more corresponding squares: the White squares d3, e3, f3, g3, and h4 correspond, respectively, to the Black squares c7, d7 e7, f6, and g6. If it is Black's turn when both kings occupy corresponding squares, Black is forced out of position.
From that I knew White would need to triangulate at some point, but the actual triangulation move was not obvious to me. Maybe in a real game I would stumble on the correct move.
The key idea is that after 1. Kb2 Kb8 Black wants to move to a corresponding square after White does. White also wants to move to a corresponding square after Black does.
Note that 1... Kb7 loses to 2. Kc3 because both players attack two corresponding squares and it is Black who has to move first. This is tricky to see.
(I'm still trying to wrap my brain around 1. Kb3 Ka7 draws. After 2.Kc3 Kb7 we have the situation described above where both players attack the same two corresponding squares, but it is White's turn. Can't White still try to triangulate? Apparently not. I need to look at this further.)
So where's the triangulation?
2. Kc2 Kc8
(2... Kb7 3. Kc3 is still winning.)
3. Kd2 Kd8
Black stays in range of b6.
4. Kc3 Kc7
Still keeping in range of b6.
5. Kd3
This is the triangulation because Black must still guard b6. Both kings are on their corresponding squares and it is Black's turn
5... Kd7
(5... Kb6 6. Ke3 wins on the kingside.)
6. Kc4.
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