King and pawn versus king endgame


The chess endgame with a []king and a pawn versus a king is one of the most important and fundamental endgames, other than the basic checkmates. It is important to master this endgame, since most other endgames have the potential of reducing to this type of endgame via exchanges of pieces. It is important to be able to tell quickly whether a given position is a win or a draw, and to know the technique for playing it. The crux of this endgame is whether or not the pawn can be promoted, so checkmate can be forced.
In the first paragraph of one of his books on endgames, Peter Griffiths emphasized the importance of this endgame:
There is simply no substitute to a clear understanding of when and how these positions are won or drawn, not only so that one can play them accurately, but in order to recognize in advance what the correct result should be. If you can do that, you can exchange off quite confidently from a more complex position.

In the positions in which the pawn wins, at most nineteen moves are required to promote the pawn and at most nine more moves to checkmate, assuming that the pawn was promoted to a queen.
Except for the section on defending and some actual games, it will be assumed that White has a king and pawn and Black has a lone king. In general, Black should place their king in the path of the pawn to try to prevent its promotion.

Rule of the square

The most basic rule is when the pawn can queen unassisted by its king. The rule of the square determines if this is possible. In this position, the pawn is on the fifth square from the queening square. A square of 5×5 squares with the queening square in one corner and the pawn in an adjacent corner can be imagined. If the black king can move into this square, he can catch the pawn, otherwise the pawn wins the race.
In this position, if it is Black's move, he can move...Kb4 and enter the square, catching the pawn. If it is White's move, the pawn advances, the square shrinks to 4×4, and the king cannot move into the square, so the pawn queens.
Even if the defending king can move inside the square of the pawn, the attacking king may be able to block it, as in the diagram from Fishbein.
Moving into the square.
and the pawn promotes.
Note that in some cases, the king can catch a pawn when he is outside the square by creating threats that must be parried, and gain a tempo. In the Réti endgame study, the white king is outside the square of the black pawn, two tempi short of catching the pawn. However, White can draw by "going after two birds at once".
If 2...h3 then 3.Ke7 or 3.Ke6 and the pawns promote together.
If 3...h3 then 4.Kd6 h2 5.c7, draw.

Key squares

If the defending king is within the "square", then the pawn cannot queen without the help of its own king. The first concept that needs to be introduced is that of the key square, also known as a critical square. A key square is a square such that if White's king occupies it, White can force the pawn to promotion, regardless of where the black king is and regardless of which side is to move, and against any defense. The key squares are relative to the position of the pawn. Whether or not the white king can reach a key square depends on the position of the pieces. Of course, even if the white king occupies a key square, accurate play is still required in order to promote the pawn.
Note that the key square is in front of the pawn. Endgame expert Yuri Averbakh said, just as a father leads his child across the road rather than pushing the child in front, the king should also lead the pawn to the queening square.

Rook pawn

A rook pawn has much less chance of promoting than other pawns. The reason is that if the opposing king can get to any square in front of the pawn, it cannot be driven away from the file, and the pawn cannot queen. Black can always draw if he can reach the c8-square for an a-pawn, or the equivalent f8 for an h-pawn, except for the position in the next diagram, with White to move. Therefore, an advanced rook pawn generally has two key squares: b7 and b8 for an a-pawn, and g7 and g8 for an h-pawn. The key squares are indicated by the black dots in the position in the diagram.
If White's king can reach either of the two key squares, he can keep Black's king away and the pawn will promote. If the Black king can reach any of the squares marked with a dot or an "X", it stops the pawn.
The pawn can also promote in the position on the right, after
However, in practice most of the time the black king can stop a rook pawn because it is usually close enough that the white king cannot prevent it from getting in front of the pawn.

Examples from games

The game Oscar Panno–Miguel Najdorf, Buenos Aires 1968, continued
and White won because the white king can reach the key square g7. Black resigned in light of
If 61...Ke6, then 62.h4; not 62.Kg7 because 62...Kf5! wins the pawn.
Moving to a key square, the only move to win.
The only move to win. The king protects the pawn as it promotes.
If Black was to move in this position, he would draw by reaching the f8-square and preventing the white king from getting to a key square, and the pawn cannot promote.
This position from a game between Gedeon Barcza and future world champion Bobby Fischer was a draw.

Pawns other than rook pawns

Pawns other than rook pawns have a much better chance of promoting. If the pawn is on the second, third, or fourth rank, there are three key squares – the square two squares in front of the pawn and the squares to the left and right of that square. The key squares are indicated by the black dots, for example see the diagram on the left. If the pawn is on the fifth or sixth rank, there are six key squares: the square in front of the pawn and the squares to the left and right, as well as the square two squares in front of the pawn, and the squares to the left and right of it, see the diagram in the middle. When the pawn is on the seventh rank, the key squares are the squares on the seventh and eighth rank that touch the pawn's square.
An easy way to remember the key squares is to note that if the pawn is not beyond the midpoint of the board, there are three key squares that are two ranks ahead. If the pawn is on the fifth or sixth rank there are six key squares on the two ranks in front of the pawn. If the pawn is on the seventh rank, the adjoining squares on the seventh and eighth ranks are key squares.
Once White's king occupies a key square he can keep the opposing king from blocking the advance of the pawn, as will be shown below.

Knight pawn exception

There is an exception to the key squares rule with a knight pawn, the black king in the corner, and Black to move. In the diagram on the right, with the white king on either the square indicated or the square marked by "x", the position is stalemate if Black is to move. This is sometimes known as the b- pawn trap.
In this position, the best move is 1.Kh6! If
Now if 2.g6+ then 2...Kh8! draws, or
does not work for White because 3.g6?? is stalemate. White must play
getting back to the original position, followed by 4.Kh6.
This position came up in a game between Harry Golombek and Arturo Pomar. White made a different move which takes longer to win and has to avoid the exceptional position:

Any key square by any route

It is important that White wins if he gets their king to any key square and the path to a key square is not always direct. For instance, in the diagram, the key squares for White are b5, c5, and d5; however, Black can prevent the white king from reaching a key square directly. For example:
taking the opposition.
However, the white king can reach a key square by going on the other side of the pawn:
Opposition, and Black is in zugzwang.
or
and the white king has occupied a key square and has a winning position.

Opposition

The second concept needed is opposition – when two kings face each other with only one square in between, the side with the move may have to move the king away and allow the opposing king to advance. The other king has the opposition.
However, Averbakh pointed out that the opposition is a means to an end; the end is penetration to a key square. If you can penetrate without the opposition, then do so. In this diagram, White should seize a key square by playing:
and moving to a key square on the next move. Taking the opposition by 1.Ke4 draws.

Rules

If the pawn is not a rook pawn some rules apply:
The reason is that if the black king alternates between those two squares, he can keep the white king from getting to a key square. The exception is the position in the diagram, and only if White is to move, because of
Black was in zugzwang.
followed by
Otherwise, if the black king stays on one of those two squares, he keeps the white king from occupying a key square.
In positions in which fewer than two of the conditions are met, it may or may not be possible to get to a position meeting at least two of the conditions, depending on the position of the pieces and who is to move. In such positions, if the attacker can get to a position that meets two conditions, he wins. On the other hand, the defender may be able to prevent the attacker from getting to such a position. Recall that rule 1 above gives a condition which draws for Black.
There are three cases to be considered. In any of these three cases, the white king is able to force his way onto a key square and thus reach a winning position. Accurate play from that position is still needed to win the game.

Case 1, conditions (b) and (c) are met

Conditions and are met in this diagram, if it is Black's move. Black cannot prevent the white king from reaching the key square d7.
Black was in zugzwang.
followed by
and White wins.
This position illustrates an important rule of thumb: If the White king is on its sixth rank, the pawn must be advanced to the seventh rank without giving check.

Case 2, conditions (a) and (c) are met

Conditions and are met in this diagram, with either side to move.
If it is Black's move in this diagram, the game could go
Black was in zugzwang.
and White wins because the pawn advanced to the seventh rank without giving check, as in the position in the diagram in the previous section.
If it is White's move in this diagram,
and Black cannot prevent the pawn from queening.
White must take a little more care with a knight pawn. If White moves 1.Kf6, Black can reply 1...Kh7 and White must back up with 2.Kf7 Kh8 and proceed as above, because 2.g6+? Kh8! 3.Kf7 is stalemate.

Case 3, conditions (a) and (b) are met

Conditions and are met in this diagram, if Black is to move. The game could continue
White takes the opposition. White's king has reached the sixth rank before the pawn; 6.e6?? Kf8 draws.
and White wins. There are several other variations, depending on Black's moves.

Example from Maróczy vs. Marshall

In this example from Géza Maróczy–Frank Marshall, Monte Carlo 1903, Black to move gets their king in front of the pawn with the opposition:
and the game could continue:

Case 4, all three conditions are met

Of course, the ideal situation is when all three conditions are met. In this diagram, if Black is to move all three conditions are met and White wins easily:
and the pawn will promote.
If White is to move in this position, then conditions and are met, so White wins:
etc., as above.
This emphasizes the importance of getting the king to the sixth rank in front of the pawn. If this configuration is achieved, White wins no matter which side is to move.

Exception – rook pawn

For a rook pawn, it is possible for Black to draw even if all three conditions are met. In the diagram, all three conditions are satisfied but it is a draw no matter whose move it is.
If it is Black to move:
leads to either stalemate or White giving up the pawn. Or if
leads to a draw. If it is White to move:
is stalemate. Or:
leads to either White giving up the pawn or stalemate.
In both cases with White to move or Black to move, all Black needs to do is shuffle between a8 and b8 and White's king can never reach the key square b7 or b8.
In the second diagram, it is again a draw no matter whose turn it is.
If it is White's turn:
and this time it is White who is stalemated. If it is Black's turn:
and the position in the previous diagram is reached which is a draw no matter who is to play.

Defending drawn positions

Now consider defending positions when only one of the conditions of Rule 2 is met, which is not sufficient to win if the defender is able to prevent the attacker from getting a position that meets at least two of the conditions.

The king is in front of the pawn

If the king is in front of the pawn and neither of the other two conditions is met, the defense is easy.
In this diagram, with White to move, Black's king is in front of the pawn, but it is not on its sixth rank and it does not have the opposition. White draws by
taking the opposition and preventing the black king from getting the opposition or advancing to its sixth rank. Then if the black king steps to the side, White simply maintains the opposition:
If the pawn now advances, White gets to a drawn position by moving in front of the pawn.
Note that 3.Kb1 would lose to 3...Kb3 because Black now has satisfied all three conditions of rule 2.
Black to move cannot make any progress from this position; the white king simply stays on b2 or b3, unless Black advances the pawn again, in which case the king moves between b1 and b2. Black cannot disrupt this without stalemate, for instance 3...b3 4.Kb1 Kc3 5.Kc1 b2+ 6.Kb1 Kb3 stalemate.

The king has the opposition

In this diagram, with White to move Black's king has the opposition, but neither of the other conditions. White to move simply moves
and black cannot promote the pawn, for example:
The defending king must drop back vertically.
and now either the king must move away from the pawn and allow it to be captured, or move 4...Kd3 resulting in a draw by stalemate.

The king is on the sixth rank

In this diagram the black king is on its sixth rank, but with Black to move it does not have the opposition. If the Black king moves, the white king simply goes to d2 or d1. If the pawn advances, the white king moves to d1 and a draw results as above.
A player should be familiar with both the attacking and defending roles, since a wrong move by the defender may allow the attacker to get to a winning position and a wrong move by the attacker may give up one of the conditions of rule 2, resulting in a draw.

Example from Gligorić versus Fischer

In the game Svetozar Gligorić–Bobby Fischer, Yugoslavia 1959, White can get their king in front of the pawn, but he does not have the opposition and is not on the sixth rank. Black must make sure that White does not get the opposition or get the king to the sixth rank:
Any move by Black to the seventh rank loses because White can take the opposition and reach a key square. After 1...Kb8, Black draws by taking the opposition if the white king advances, e.g. 2.Kc5 Kc7! draws or 2.Kb5 Kb7! draws,.

Guidelines

gave these guidelines:
With Black to move, White wins by first occupying a key square and then by getting two of the conditions above:
The white king is on the sixth rank ahead of the pawn and White can advance the pawn.
If White is to move, Black draws:
Alternatives 3...Kd6 and 3...Kb6 also draw.
If 7...Kd8 then 8.Kd6, taking the opposition, wins.
and Black draws.

Kamsky vs. Kramnik

This position from Gata Kamsky–Vladimir Kramnik, Nice 2009, was reached after the exchange of rooks in a rook and pawn versus rook endgame. Black draws easily:
Ke8 also draws.
Taking the opposition.