King + Pawn vs King · Ending 3
Knight’s pawn stalemate resources, diagonal opposition, and the essential concept of key squares — the rules that tell us at a glance whether the pawn can promote.
We continue from the knight’s pawn preview of the previous chapter. White cannot take the opposition, but the nearby edge creates a special saving resource.
Position 1.8 · Knight’s pawn stalemate resource · White to move
FEN: 8/8/8/8/8/5kp1/7K/8 w - - 0 1
Let us have a look at the position. White cannot take the opposition. If the king moves in front of the pawn, he will have to retreat from his blocking position on the next move.
This position would be lost if Black had a central pawn, but with a knight’s pawn White can be saved thanks to a special detail.
The right move
This relative position of the kings is called diagonal opposition. Usually, diagonal opposition does not help much, but here it works because of the nearby edge.
Continuation
This move would secure promotion with any other pawn, but now the white king is stalemated and the position is drawn.
Variation
When the pawn has not reached the 6th rank yet, the analysis grows in complexity, but there are very clear rules. If we know them, we can play the ending accurately and quickly know whether the pawn promotes or not. The essential concept here is that of key squares.
When the pawn is on the 5th rank, its key squares are the three squares directly in front of it. Since the white king has reached one of them, White wins.
Position 1.9 · Key squares for a 5th-rank pawn · White to move
FEN: 5k2/8/4K3/5P2/8/8/8/8 w - - 0 1 · Key squares: e6, f6, g6
The marked squares e6, f6, and g6 are the key squares for the pawn on f5. The white king already occupies one of them, so White wins.
Winning move
Continuation
The black king has retreated from the pawn’s path. Now White secures promotion.
Main line
Now the pawn’s path is clear.
Once again, the knight’s pawn poses extra difficulties, but the key-square rule still applies. We just need to be slightly more careful.
Position 1.10 · Knight’s pawn · White to move
FEN: 7k/5K2/8/6P1/8/8/8/8 w - - 0 1
The king must go to the other side to avoid annoying stalemate tricks.
Winning move
The king must go to the other side to avoid annoying stalemate tricks.
Note: 1.Kf6 does not throw away the win, but after accurate defence White may need to return to the starting position.
Main line
Now the king is on the correct side of the pawn, so promotion runs smoothly.
Continuation
If the pawn has not reached the 5th rank, its key squares are two ranks ahead. For example, for a pawn on the 4th rank, the key squares are on the 6th rank. The rule still applies: if the white king occupies one of those key squares, the pawn promotes.
Position 1.11 · Key squares when the pawn has not reached the 5th rank · White to move
FEN: 4k3/8/8/8/3PK3/8/8/8 w - - 0 1 · Key squares: c6, d6, e6
The marked squares c6, d6, and e6 are the key squares for the pawn on d4. In the diagram position, the white king can reach one of the key squares, but sometimes opposition makes the fight for those squares harder.
Winning move
White heads for the key square c6.
Main line
Once White has occupied one of the key squares, the pawn promotes.
Continuation
This position introduces the distant opposition. In the source diagram, the key squares are marked on the third rank: b3, c3, and d3.
Position 1.12 · The distant opposition · White to move
FEN: 8/8/8/1kp5/8/8/8/K7 w - - 0 1 · Key squares: b3, c3, d3
When the kings are far apart, opposition can still decide who reaches the key squares first. The detailed explanation continues in the following part. For now, this is the transition into the next lesson.