A lasting weakness cannot easily move away
A piece can usually retreat; a pawn structure is harder to repair. Doubled, isolated and backward pawns may therefore provide long-term targets. But a label alone does not make a pawn weak. An isolated pawn can give space, open files and a dangerous advance. A backward pawn may be perfectly safe if you cannot attack it.
Ask three questions: Can the weakness advance or be exchanged? Can I attack it more times than it can be defended? Will attacking it improve my pieces? If the answer to all three is no, choose a more useful plan.
Recognise common pawn targets
An isolated pawn has no friendly pawn on an adjacent file. It may need piece protection, but often provides open files and active squares. A backward pawn cannot safely advance and sits behind neighbouring pawns; the square in front of it is often an excellent blockade. Doubled pawns can be weak because they cannot protect each other, yet they may control important squares or open a rook file.
A pawn becomes most vulnerable when it is fixed. If you can stop it advancing, your pieces can gather without the target disappearing. A pawn move such as h4 can fix an enemy pawn on h5, but also creates squares behind your own pawn, so check the cost.
A weak square cannot be protected by a pawn
A square is weak when enemy pieces can occupy it and your pawns cannot chase them away. Central squares are especially valuable because a knight there may attack both wings. The hole in front of a backward pawn often combines a weak square and a weak pawn into one plan: blockade first, attack second.
Before installing a piece, check whether the opponent can exchange it. An outpost occupied by a knight is less impressive if their bad bishop can trade for it immediately. You may first need to remove the exchanging piece.
Restrict, pile up, then break through
The usual order is: fix the target, blockade it if necessary, improve your pieces, add attackers and only then calculate a way to win it. Your opponent will seek counterplay, so do not let every piece become tied to one pawn while your king is attacked elsewhere.
The principle “two weaknesses” matters. One weakness can often be defended. If you create a second target on the other side, the defender may not have enough active pieces for both. Switching sides is often stronger than adding a fourth attacker to a fully defended pawn.
Worked position: blockade before attack
Interactive board: the d5 square and d6 pawn
Find the square that makes the pawn weakness harder to defend.
When you own the weakness
Defend actively. Advance or exchange the weak pawn if it is safe, create counterplay on another file, trade the opponent’s best blockader, or simplify into an ending where the weakness cannot be attacked. Passive defence is sometimes necessary, but it should not be your first choice.
In your next game, do not merely announce “that pawn is weak.” Complete the sentence: It is weak because it cannot move, and I can attack it with ___ while preventing ___.