Pawn Chains

A pawn chain is a diagonal line of pawns where each pawn (except the very back one) is defended by the pawn immediately behind and to the side of it. The pawn at the very back of the chain is called the base -- it's the one holding the whole structure up, since it isn't defended by another pawn. The pawn at the very front is the tip, or head, of the chain.

Kmoch's classic advice is that the right way to attack a pawn chain is at its base, not its tip: undermining the base pawn (usually by attacking it with a pawn of your own, or trading it off) can cause the whole chain to collapse, whereas attacking the tip just runs into the chain's own defenders. This idea shows up constantly in openings like the French and King's Indian Defense, where long locked pawn chains define the entire strategic plan for both sides.

A single pawn with no diagonal defender or defendee doesn't count as a chain by itself -- it takes at least two connected pawns to form one.