Why are doubled pawns in this case particularly devastating? There is a case where the opponent can inflict a double pawn on us

[FEN "4k3/ppp2ppp/3p4/4p3/4P3/2PP4/P1P2PPP/4K3 w KQkq - 0 1"]


Why is this kind of double pawn particularly devastating for white? I see white is okay, white can try d4 pawn break, or Rb1.

Or am I wrong? Can somebody explain why this position is not favourable for white?

This pawn structure can also arise from Nimzo Indian

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.a3 Bxc3+ 5.bxc3
I first need to note that there is a fairly large difference between the structure in your first diagram and the one reached in the Nimzo-Indian line: in the first diagram, white has not yet played d4. This gives him the option of playing c4 and c3, which is actually quite a strong structure as the d4 square, which would normally be weak with pawns on c4, d3 and e4, is defended by the c3-pawn.

That being said, I don't agree with the assessment that this is an uncommonly bad case of doubled pawns for white. While doubled pawns are, in general, unfavorable for the side that has them, their existence is usually not enough to significantly change the evaluation of a position. In fact, the second line gives us an approximation of how much opening theory thinks that white's structure has been crippled: about the difference between a bishop and a knight.

I wrote the above and then realized that I may have misinterpreted your question. You may be wondering why white's structure in the first diagram is worse than black's.

The doubled-pawn structure is a slight disadvantage and has both plusses and minuses which may be exploited in a given piece configuration by either side. One plus would be the possibility which I mentioned in the first paragraph. Your idea of putting a rook on b1 is another option, although that may be mitigated by black playing b6. White pushing d4 is also an idea, although it may not be so favorable here because a capture on e5 would leave the c-pawns isolated.

Black's structure is better, though, because each of his pawns on the queenside has the potential to be defended by another pawn rather than a piece. White, by contrast, will always have two pawns not defended by pawns: the a-pawn and at least one c-pawn. The attention that white's pieces will have to use defending the pawns on average will outweigh the other considerations.