Weak Pawns As Targets
Seirawan Strategy Example #2
Winning Chess Strategies, Diagram 85, p139
This example is all about "Acceptable" Doubled Pawns; when, despite your knowledge that the Doubled Pawn structure is usually thought to be Weak, the Doubled Pawns in the following situations, are actually NOT as Weak as their structural term suggests.
Acceptable Doubled Pawns are usually not Weak, due to:
The ChessFlash viewer gets a bit overcrowded in this example, as there are 3x examples of Acceptable Doubled Pawns (two in Black's army; one in White's army). So, I've created images of those three separate positions, which you can see beneath the ChessFlash viewer.
3x Examples of Acceptable Doubled Pawns
Acceptable Doubled Pawns #1
Black's b-File Pawns (b7,b6)
After: 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Bc4 Bc5 5.O-O O-O 6.d3 d6 7.Be3 Bb6 8.Bxb6 axb6
Seirawan says Black's Doubled b-File Pawns are NOT WEAK. The b7-Pawn is heavily covered by b6-Pawn and Nc6, and defended by Bc8; while the b6-Pawn is defended by the c7-Pawn.
In addition, Black has the advantage of the Ra8 on the Half-Open File (a-File). After 7...Bxe3, this move leads to White having Doubled Pawns on the e-File.
Acceptable Doubled Pawns #2
White's e-File Pawns (e3,e4)
After: 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Bc4 Bc5 5.O-O O-O 6.d3 d6 7.Be3 Bxe3 8.fxe3
Seirawan says that White's Doubled e-Pawns are acceptable as they contribute to White's fight to Control the Center.
Instead of having the f2-Pawn in a passive role, White lets it go to e3, deliberately weakening the Pawn Guards surrounding his Castled King, in order to have 3x Pawns attacking three of the four Center squares, which betters Black's two Center Pawns (d6 & e5).
White's Control of the Center should give him sufficient advantage in the Opening phase, to try and convert it into a decent Middlegame advantage, which should, in turn, compensate for the slightly Compromised King-side position (note the 2-Pawns in front of White's King, versus Black's 3-Pawn Guard still intact in front of their King).
Acceptable Doubled Pawns #3
Black's c-File Pawns (c7,c5)
After: 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Bc4 Bc5 5.O-O O-O 6.d3 d6 7.Be3 Bg4 8.Bxc5 dxc5
Seirawan says Black's Doubled c-Pawns are safe, as an attack by White's b-Pawn (9.b2-b4) would enable 9...cxb4, leaving Black's Pawn Doubled on the b-File (b7,b4), but forcing White's Nc3 to move from its favorite defensive square, while also being protected by Black's Nc6.
Alternatively, an attack by White's d-Pawn (9.d3-d4) would enable Black to dissolve the Doubled Pawns, with 9...cxd4. This would give Black the advantage of an Advanced Chain (e5,d4), which would be defended by Black's Nf6, and like the previous outcome, would also force White's Nc3 to evacuate its favorite defensive position.