Critical Squares in Pawn Endgames: the squares that decide

If opposition tells you how to maneuver with the king, critical squares tell you where you need to go. They’re the squares that, if your king occupies them, guarantee that the pawn will promote. No matter what.

Let’s see which ones they are and how to use them.

What are critical squares?

Critical squares (also called key squares) are the three squares that are two ranks ahead of your pawn, on its own file and on the two adjacent files.

For example, if your pawn is on e4, the critical squares are d6, e6, and f6. If your king reaches any of those three, the pawn promotes. The defender can’t prevent it.

Why do they work? Because if your king is two ranks ahead of the pawn, it has enough room to win the opposition, advance, and escort the pawn to the eighth rank. The defending king doesn’t arrive in time to block all the routes.

The rule based on the pawn’s position

The critical squares change slightly depending on how advanced the pawn is:

Pawn on the second, third, or fourth rank

The critical squares are the three two ranks ahead. Example with pawn on d3: critical squares = c5, d5, e5.

If your king reaches any of the three, the pawn promotes.

Pawn on the fifth rank

Here the critical squares expand. In addition to the three on the sixth rank (two ahead), the three on the seventh rank also count. That is, with a pawn on e5, the critical squares are d6, e6, f6, d7, e7, and f7.

The pawn is so advanced that the king has more promotion routes.

Pawn on the sixth rank

With the pawn on the sixth, the critical squares are the three on the seventh and eighth ranks. At this point the pawn is two steps from promoting and the king only needs to maintain the pressure.

The rook’s pawn exception

With a rook’s pawn (the “a” or “h” file), the critical squares are reduced to two instead of three, because the edge of the board eliminates one adjacent file.

That makes it much harder to reach a critical square, and explains why rook’s pawn endgames tend to end in draws: the defender has fewer squares to cover.

How to use critical squares in practice

1. Identify your pawn’s critical squares

Look at where your pawn is and calculate the three squares (or two, if it’s a rook’s pawn) that are two ranks ahead. Those are your target.

2. Bring the king to a critical square

Use opposition and, if necessary, triangulation to advance your king toward the critical squares. Don’t advance the pawn until your king is well placed.

3. Advance the pawn once the king is in position

Once your king occupies a critical square, the pawn advances with a guaranteed promotion. The order is always: king first, pawn after.

Critical squares and opposition

Critical squares and opposition are two sides of the same coin:

• Critical squares tell you where to go.
• Opposition tells you how to get there.

If you understand both concepts, you can solve practically any king and pawn vs king endgame without having to calculate move by move. It’s enough to know whether your king can reach a critical square or not.

Practice critical squares

Keep learning

• Opposition — how to maneuver with the kings
• King and pawn vs king — the endgame where it all applies
• Zugzwang — the mechanism that makes it work
• Triangulation — how to reach the critical squares
• Pawn endgames — all the articles in this section