Pawn chain
A diagonal line of pawns of the same colour, each defending the next — the spine of many middlegame structures.
A pawn chain is a diagonal sequence of pawns of the same colour, each protected by the one behind it. The chain’s base is the rearmost pawn — the only one in the chain that is not defended by another pawn. The chain’s head is the most advanced pawn, pointing into enemy territory and restricting the opponent’s pieces.
The pawn chain is the central structural idea in several openings. The French Defense produces the classic chain after 1.e4 e6 2.d4 d5 3.e5: White’s chain d4–e5 against Black’s e6–d5. The King’s Indian Defense produces a similar chain after Black plays …e5 and White plays d5: the chains face each other on both sides of the board, with one player attacking the kingside and the other the queenside.
The classical advice for attacking a pawn chain — first articulated by Aron Nimzowitsch — is to attack the base. The head is well defended; the middle pawns support each other; the base is the only pawn that pieces alone must defend. If the base falls, the chain collapses.
In practice, both attacking the base and pushing past the head are valid plans. The French Defense’s whole middlegame turns on whether Black can break the chain with …f6 (attacking the head) or …c5 followed by pressure on d4 (the base).