Pawn endings

A game on lichess.org, 2014. On the board are the kings and a single white pawn on c6. The black king stands next to the promotion square, on b8. If White plays inaccurately, Black will hold the draw. White to move.

One king move decided whether White wins or draws. That is how the pawn endgame works: there are hardly any pieces, there are few moves, and any of them can decide the result. On the other hand, it can be calculated to the end. In this chapter we look at the rules that help you calculate quickly: the opposition, key squares, zugzwang and the breakthrough.

The king in the endgame

In the middlegame the king hides behind its pawns. In the endgame, once the queens and most of the pieces are gone, it becomes a strong piece: it takes pawns, supports its own and keeps the enemy king out. The first rule of the pawn ending is to bring the king to the centre or to the pawns as quickly as possible. Whoever has the more active king usually wins.

An active king does several jobs at once. It stands in the centre and reaches either wing in one or two moves. It attacks the opponent's pawns, and they have to be defended. It keeps the enemy king away from its own pawns. That is why in a pawn ending the king often goes forward on the very first move, while the pawns wait: their moves will be useful later as spare tempi. The defending side does the same. If its king stands to one side, it must return to the pawns as quickly as possible, even at the cost of a pawn on the other wing.

The second rule is to count. In a pawn ending there is no room for general considerations: if you promote a move earlier than your opponent, you win; a move later, and you lose. Before every move, recount how many moves each side needs to promote a pawn or to take an enemy one. The rule of the square from the chapter on the passed pawn is one of these quick ways of counting.

That is exactly why going into a pawn ending is a serious decision. While there are pieces on the board, a mistake can be put right. Once the last piece has been traded, only counting is left, and the pieces cannot be brought back. Strong players calculate a pawn ending to the end before they trade into it.

The opposition

Kings cannot stand next to each other: there is always at least one square between them. When the kings stand on the same file or rank with one square between them, they are said to be in opposition. Each takes three squares in front of the other. The side that “has” the opposition is the one that made the last move: the opponent has to move and give way.

The opposition can also be distant: the kings stand on one line with three or five squares between them. The rule is the same: if there is an odd number of squares between the kings and it is the opponent's move, you have the opposition. Distant opposition is used to prepare the close opposition in advance. And when the kings stand in close opposition, the attacker often outflanks: they step to the side, and the defending king can no longer block their way.

For example, the white king stands on e2, the black king on e8, and it is Black to move. There are five squares between the kings, so White has the opposition. Wherever the black king goes, the white king moves to meet it so as to stand opposite it again with an odd number of squares in between. When the kings come together, White will have the close opposition.

The defending side uses the opposition too. Its king stands in front of the pawn, and its task is the reverse: every time the attacking king approaches, it steps opposite it. As long as this works, the attacker cannot get forward. So in a pawn ending both sides watch the same thing: whose turn it is when the kings end up facing each other.

In the next position the white pawn is on f4. The white king needs to get forward, and the black king on g7 is in the way. Find the move that gives White the opposition.

Key squares

The opposition is a tool. The attacker has one goal: to bring their king to a square from which the pawn promotes whatever the defence. Such squares are called key squares. If the attacking king has reached a key square, the position is won, whoever is to move.

Key squares are easy to find. For a pawn on the second, third or fourth rank they are the three squares two ranks in front of it: for a pawn on e2 they are d4, e4 and f4; for a pawn on e4, d6, e6 and f6. For a pawn on the fifth or sixth rank there are six key squares: the three directly in front of it and the three one rank further on. Rook pawns are a special case, covered below.

The rule of key squares gives a simple piece of advice: the attacking king should go in front of the pawn. A pawn does not guard the squares in front of itself. The king, from a square ahead of the pawn, covers its path and keeps the enemy king out. If the pawn has run ahead on its own, the opponent's king steps in front of it, and winning becomes hard. So the pawn is advanced only when the king has cleared the way for it.

Check the rule on a simple example. The white pawn is on e4, the white king on e6, the black king on e8. The king is already on a key square, and it does not matter whose move it is. If Black is to move, the white king goes to d7 or f7 and the pawn promotes. If White is to move, White makes a king move to the side, for example Kd6, and after the black king retreats the white king comes forward again.

Now it is clear what happened in the first position of the chapter. The key squares of the c6-pawn are b7, c7, d7 and the three squares on the eighth rank. The opposition helped the white king reach b7 or c7, and the black king could not stop it. See how this works when the white king stands further from the key squares.

Now win it yourself. The white pawn is on e2, and its key squares are d4, e4 and f4. The engine plays against you, and it defends precisely.

The defence is built on the same rules. The defending king must stand in front of the pawn and keep the attacker off the key squares. When the pawn advances, the defender steps straight back and takes the opposition as soon as the attacking king reaches the sixth rank. Try to hold the draw with Black.

With a rook pawn everything is different. If the defending king has reached the corner in front of an a- or h-pawn, it is almost always a draw, even when the attacking king is close by: the corner square cannot be outflanked, and any attempt to drive the king out of the corner gives stalemate.

A rook pawn wins only if the defending king is cut off from the corner and cannot get there in time. So when defending against an a- or h-pawn, head for the promotion square first. The attacker, on the contrary, should cut off the enemy king with their own early, while the pawn is still far back.

Zugzwang

In chess you cannot pass. Usually that does not matter: there is always a useful move. But in pawn endings there are positions where every move makes things worse. Such a position is called zugzwang, from the German for “compulsion to move”. The opposition is a special case of zugzwang: the king has to give way simply because it must move.

The first position of the chapter is zugzwang too. After Kb6 Black would like to stay where they are: then the white king would not get forward. But Black has to move, and every move of the black king opens the way for the pawn or the king.

Sometimes the turn to move can be passed to the opponent by a king manoeuvre. If the attacking king can walk round a triangle in three moves while the defending king in the same area can only step back and forth, the attacker gains a tempo and puts the opponent in zugzwang. This technique is called triangulation.

There is also mutual zugzwang: a position in which whoever is to move loses, whichever side that is. In such positions one tempo turns the result upside down. That is why spare pawn moves are so valuable: a pawn that can still move lets you pass the turn to the opponent. Save such moves for the right moment and do not spend them without a reason.

Zugzwang also decides positions with several pawns. Look at the next one: each side has three pawns, but the black king is stuck on a3, and the white pawn on b3 can still move.

The breakthrough and the outside passed pawn

When both sides have pawns on the same wing, a passed pawn can sometimes be created by sacrificing pawns. This is the breakthrough. The classic example: three white pawns on the fifth rank against three black pawns on the seventh. The kings are far away, and White breaks through by force.

A breakthrough works only if the opponent's king cannot reach the new passed pawn in time. So before the sacrifice, count: how many moves the pawn needs to reach the promotion square and how many the king needs to catch it. The rule of the square helps here again.

When each side has several pawns, a passed pawn is usually created with a majority. Two pawns against one on a wing give a passed pawn, and so do three against two. Start with the pawn that has no enemy pawn in front of it: it is called the candidate. The other pawns support it, and after the exchanges the candidate becomes a passed pawn. Meanwhile the king holds the opponent's pawns on the other wing.

When both sides have passed pawns, a race begins: who queens first. Here it is not enough to count the moves to the promotion square. Check whether the opponent's new queen will appear with check, whether it will take your queen straight after promotion, and whether it will block your pawn's path. The pawn race is covered in the chapter “The passed pawn”.

A related idea is the outside passed pawn. If you have a passed pawn far from the others, for example on the edge of the board, the opponent has to send their king after it. While their king is busy, your king goes to the other wing and picks up the pawns there. An outside passed pawn often wins a pawn ending even with equal material: it decoys the opponent's king, and that is worth more than a pawn.

If the outside passed pawn is your opponent's, keep your king close to it and avoid needless pawn trades on the other wing. The fewer pawns are left there, the faster their king will collect them while yours is busy with the passed pawn.

How do you train pawn endings? Play them against the engine: king and one pawn, two pawns against one, pawns on one wing. Start with the positions in this chapter, then change where the kings stand. Set up a position, decide whether it is won or drawn, and check. After a few dozen such positions the opposition and key squares become a habit.

What's next

The most common endings in practice are rook endings: rooks are traded less often than the other pieces. They have their own famous positions that every chess player knows. They are the subject of the next chapter.