Two pawns of the same colour on one file. They cannot defend each other, and the file they opened is usually the compensation.
Why it matters
Two pawns on the same file get in each other's way. They cannot defend one another, the back one is often stuck, and together they cover fewer squares than two pawns side by side would.
They are not automatically bad. Doubling usually opens a file for a rook and adds a pawn to the centre, and plenty of strong openings accept doubled pawns on purpose in exchange for exactly that.
See it on a board
White's pawns on c2 and c3 are doubled. In return the b-file is open for the rook, which is the trade most openings that allow this are making.
Checked: the position really has the feature described.
How to play it
- When deciding whether to allow them, ask what you get: an open file, a stronger centre, or the bishop pair.
- If you have them, use the file they opened and try to undouble with a pawn break.
- If your opponent has them, blockade the front pawn and attack the base, and avoid letting them trade the back one off.
At each level
The same idea, said the way it is taught at each age.
Pawn · ages 3–6
Two of your pawns on the same line cannot protect each other. It is usually a small problem, not a disaster.
Knight · ages 4–6
Ask what the doubling bought. An open file and the two bishops is a fair price; nothing at all is not.
What goes wrong
- Avoiding doubled pawns at the cost of development or the bishop pair.
- Assuming doubled pawns are weak when they control extra central squares and no file is open against them.
Questions people ask
- Are doubled pawns always a weakness?
- No. They are a weakness in an endgame, where they cannot create a passed pawn easily, and often an asset in a middlegame, where the open file and extra central control matter more.