How doubled pawns arise
A pawn can only change file by capturing, so doubled pawns are always the result of a capture. Common examples come from the opening: in the Nimzo-Indian after Bxc3+ bxc3, White has pawns on c3 and c4, and in the Exchange Variation of the Ruy Lopez after Bxc6 dxc6, Black has pawns on c7 and c6.
When there is a choice of recapture, the usual guideline is to capture towards the centre, which keeps pawns closer to the middle of the board, but it is a guideline and not a law.
Why they are a weakness
Doubled pawns cannot defend each other, and the front pawn blocks the rear one, so the pair has less mobility than two pawns on neighbouring files. If they are also isolated, with no friendly pawns on the files next to them, they can be very hard to defend.
The biggest cost often shows in the endgame. In the Exchange Ruy Lopez, White's four kingside pawns against three can produce a passed pawn, while Black's queenside majority, with its doubled c-pawns, cannot do the same by force. This is why White is usually happy to exchange pieces in that line.
When doubled pawns are acceptable
Doubled pawns often bring compensation. The capture that doubles them opens a file next to them, such as the b-file after bxc3, and the doubled pawns can control useful central squares; a pawn on c3 supports d4. The opponent may also have given up a bishop to create them, leaving the bishop pair.
Judge them by the position. Doubled pawns that are fixed, attacked and hard to defend are a serious problem; doubled pawns that are well protected and control key squares may be no weakness at all.
Common mistakes
- Treating all doubled pawns as bad and avoiding useful captures, even when the recapture opens a strong file.
- Heading for a simplified endgame while you have doubled pawns that cannot be defended.
- Attacking doubled pawns before they are fixed, which gives the owner time to advance and trade them off.
Questions about doubled pawns
Are doubled pawns always bad?
No. They are a structural weakness, but open files, central control or the bishop pair often make up for them.
Should you recapture towards the centre?
As a rule of thumb, yes, because central pawns control more important squares. The concrete position always decides.
What are tripled pawns?
Three pawns of the same colour on one file, the result of two captures onto that file. They are usually a serious weakness.