This discussion applies to weak pawns in the middle game just as much as weak pawns in the endgame. A weak pawn is one that cannot be defended by another pawn. These types of weaknesses must be handled differently depending on the stage of the game we are in. In the middle game, the activity of the pieces is the most important thing, but when pieces start to get traded off, positional factors start to become more important.
For example, in positions with isolated pawns, the side with the pawn seeks activity and strong squares, while the opponent attempts to exchange pieces to get a favorable endgame.
Even though weak pawns can be very vulnerable, a good technique is required to defeat them. First, it is important to blockade the pawn. Mobile pawns can be dangerous, even if they are isolated or weak. After blockading a pawn, we can start attacking it. It is important to play actively and create threats, to force the opponent to create weaknesses in his camp.
Sterk vs. Grau
In this position, despite the material equality, Black has an advantage because White has three pawn islands, while Black has only two. Black played actively in this position to hamper’s White development and improve his position.
15. …Nc3! With the idea of playing Ne4 (or Na4) and Nc5.
16. Na3 Bd7
17. Nb1 The knight on c3 is strong and White wants to trade it, but we have to avoid this. Na4
18. Be2 Bc6
19. 0-0 Rfd8 Both sides are developing their pieces logically. The pawn on c4 is practically blocked because it can’t be advanced.
20. Rd Rxd1
21. Bxd1 Nb2! Hampering White’s development.
22. Be2 Rd8
23. Kf1 Kf8
24. g3 White is in a cramped position. He cannot play Nc3, because Black can reply with Rd2. Black is centralizing his king, while White is still trying to untangle. Ke7
25. Na3 Na4
26. Ke1 Nc5
27. Rc1 a6 Stopping Nb5 ideas.
28. Rc3 Ne4
29. Rc2 Ng5! Practically getting the bishop on e2 for the knight (after Nf3+) and creating nasty threats on the king afterwards (e.g. Rd1).
30. Nb1 Nf3+
31. Bxf3 Bxf3
32. Rd2 Rc8! Now the pawn is lost because if
Rc2 then Be4!
33. Rc1 Bd5
34. Nd2 b5 and Black is a pawn up.