Identifying weak squares

[Henk]

There are also positions when opponent has a knight on a very weak square of yours. But knight cannot do anything there and is misplaced.
For all is happening on the other side of the board.

[Look]

I am trying to establish what is deemed as the "official" definition of a weak square, and what is actually a weak square. So far, I am getting the definition to be a square is weak if it is on rank 3 or 4 in your own half of the board and you can never now, or in the future protect that square with a pawn, yes?

And for my unofficial definition, a weak square is on a continuum where it is weakest when it cannot be protected by a pawn or Bishop, it is slightly weak when it is protected by a Bishop (for example) and not weak when it can be protected by a pawn, and strongest when protected by a pawn and pieces.

Lets consider an example:

[d]8/6pk/8/6Qp/4p2P/3p1qP1/5P2/6K1 w - - 3 50

Here g4 is a weak square for white. If he plays g4 , he will lose that pawn. If you correctly identify weak squares , you can count them. The more weak squares one has, the bigger eval penalty for that player.

[mvanthoor]

I am trying to establish what is deemed as the "official" definition of a weak square, and what is actually a weak square. So far, I am getting the definition to be a square is weak if it is on rank 3 or 4 in your own half of the board and you can never now, or in the future protect that square with a pawn, yes?

Yes.

And for my unofficial definition, a weak square is on a continuum where it is weakest when it cannot be protected by a pawn or Bishop, it is slightly weak when it is protected by a Bishop (for example) and not weak when it can be protected by a pawn, and strongest when protected by a pawn and pieces.

The square is the lowest in the order of positional elements in chess, behind the diagonal/file/rank, center, opponent's half of the board. A rook can control an entire file starting at your half of the board right down to the opponent's half, just as your bishop on b2 can see g7 if the position is open enough. The knight is best placed in the center, or just beyond it, towards the opponent's position.

Therefore it is very detrimental if you have to keep a square covered by one of your pieces, because that piece can then no longer do what it does best. Rooks control files and ranks, bishops control diagonals, the knights function like an octopus within the opponent's half of the board, and the queen can control the entire board if she's in the center. You don't want to have a piece locked down to the defense of a square.

[Jon12345]

You don't want to have a piece locked down to the defense of a square.

And what about those squares that are neither defended by a piece or pawn e.g. f4, g4 and h4, when White has pawns on f2, g2, and h2? If a square is weak because it means a piece will have to defend it, then why are f4, g4 and h4 not weak? Perhaps there is an additional nuance, which is to say temporarily weak vs permanently weak.

[mvanthoor]

You don't want to have a piece locked down to the defense of a square.

And what about those squares that are neither defended by a piece or pawn e.g. f4, g4 and h4, when White has pawns on f2, g2, and h2? If a square is weak because it means a piece will have to defend it, then why are f4, g4 and h4 not weak? Perhaps there is an additional nuance, which is to say temporarily weak vs permanently weak.

Those squares are not weak.

If black lands a knight on g4, you can play h2h3 (or if need be, f2f3), and the knight has to move or (probably) get captured. If you already played f2f4 and h2h4 earlier, g4 is weak because you can never kick the knight away from there. The best thing you can do is trade it.

[Henk]

Knight on f4 can be deadly. g2g3 may make it even worse.Only thing you can do is exchange the knight.

[hgm]

The point is that the evaluation should score persistent traits of the position, i.e. strategic features. Tactics should be left to the search.

Now whether a square is attacked or can be attacked by a Knight is a tactical feature. It might not be attacked now, but it could very well be attacked on the next move. In that case the fact that it is not attacked isn't worth very much. It is not persistent.

Squares that can never be attacked by Pawns (through non-capture moves) are a persistent feature, though. Even if a capturing Pawn could be aimed at the square, we don't count that, because it is very unlikely the opponent will allow us to make the necessary capture. After all, captures cannot be made without some opponent consent. It takes two to capture!

The color of a Bishop is a persistent feature too. So squares where one of your pieces cannot go because it is of the other shade than you rBishop is on, are somewhat weak too. But attacking it by a Bishop interdicts much less strongly than attacking by a Pawn, and is more costly (in terms of tying up a more valuable piece), so this type of weakness doesn't have a large value.

[Jon12345]

I've thought of two additional scenarios that I am unclear on.

1. If you have a fianchetto structure with pawns on f2, g3 and h2, and a Bishop on h3, is h3 still considered a weak square, even though it has a piece on it?

2. What about if you have pawns on e2, f4, g4, and h4...does that mean g3 is considered a weak square, or is that not a weak square since it is behind a phalanx of pawns?

[mvanthoor]

1. If you have a fianchetto structure with pawns on f2, g3 and h2, and a Bishop on h3, is h3 still considered a weak square, even though it has a piece on it?

Yes.

2. What about if you have pawns on e2, f4, g4, and h4...does that mean g3 is considered a weak square, or is that not a weak square since it is behind a phalanx of pawns?

It's weak, but the f4, g4 and h4 setup gains a huge amount of space for your pieces to maneuver. Your pieces can defend the pawn phalanx from behind if need be. Therefore, this means that the weak g3 and h3 squares are difficult to target for the opponent.

Because pawns get traded and move up the board, getting weak squares in your camp is unavoidable. (Your opponent will also get weak squares.) The question then becomes: how much can my opponent do with those weak squares? If they are *behind* your most forward pawns, they are much easier to defend than when they are in front.

Consider the "Maroczy Bind": e4 c5 c4 Nf3 Nc6 g6.

[d]r1bqkbnr/pp1ppp1p/2n3p1/2p5/2P1P3/5N2/PP1P1PPP/RNBQKB1R w KQkq - 0 1

White gains massive control over the d5 square (the "bind"), but it makes d4 and d3 weak. Black immediately tries to target d4 by playing g6, and then fianchetto the bishop. d3 and d4 are very hard to defend because they are in front of the d-pawn. Thus you often see:

d4 cxd4 Nxd4

[d]r1bqkbnr/pp1ppp1p/2n3p1/8/2PNP3/8/PP3PPP/RNBQKB1R w KQkq - 0 1

Now the d-pawn is gone. d3 and d4 are still weak, but white still has the bind on d5, and now also has a half-open file. Later, white will play Be2, short castle, Be3, Qc2 or Qd2 to make room for a rook, and then one of the rooks to d1 to control the open file and cover d3 and d4.

d3 and d4 are weak forever, but black can't do a lot with them anymore because the rook controls the open file and white has strong control over d5.

Black will try to play e6 and d5 in an effort to break the bind and blast open the center to give the bishop on g7 a sight right down to a1, and at some point put its own rooks on d8 and/or e8.

Black will NOT play e5, because that will make d5 and d6 weak. Which white can make use of very easily, because they're in front of the d7 pawn: Nc3 is enough to enable Nc3-b5-d6, or Nb1-c3-d5, which plants a knight squarely in black's position. (Black could prevent the knight on d6 by playing a6, but that would make b6 weak...) Worse, playing e5 makes the d7 pawn backward AND blockaded by the knight if it's on d6, and the knight would be very hard to get rid of. Black can't exchange it against the dark-squared bishop, because that piece is needed on g7 as long as the queens are still on the board and white has its own dark-squared bishop. If black trades that bishop with the queens on the board and with white still having the dark-squared bishop, the game's going to be very hard to play for black. Maybe it's even game over if the black king's castled short.

The Maroczy Bind is very hard to play against with black, to the extend that the Sicilian opening saw a marked drop in popularity for some time: "For several decades, it was generally considered tantamount to a positional blunder for Black to allow the Maróczy Bind." Nowadays, good ways to play against that setup have been found, but you'll have to know them.

And all of that... with weak d3 and d4 squares from the get-go.

So... a square is weak if it can never again be defended by a pawn, but this does not mean that it can't be defended at all. As illustrated above, they sometimes can be defended easily by trading off the pawn that is behind the weak squares, opening half the file from your side. Some openings like the one above make that a point.

PS: a backward pawn is a pawn that can never again be defended by a friendly panw, and it can't move forward without being captured []by an enemy pawn. The square in front of the backward pawn is _by definition_ a weak square for the side with the backward and an outpost for the other side.

[d]4k3/8/3p4/4p3/4P3/8/3K1P2/8 w - - 0 1

d6 is backward, and f2 would become backward if white would play f2f3. White is better here: White will either play Ke3 and f4 to get rid of its own possibly backward pawn while keeping black's. Black must capture; if he doesn't, white will push the pawn past to f5 creating a covered passer, and it's probably game over. With careful play, black can hold this position.

[Jon12345]

An excellent exposé about the Maroczy Bind, which I enjoyed reading. It made me more convinced that calling something a weak square using the official definition, and how weak that square actually is are sometimes two different things.

If you had your pawn still on d2, d3 and d4 are weak. But if you advanced it to d4 and exchanged it off, you have more control over d3 and d4. So, someone could say, "But the definition of a weak square is where it cannot be defended by a pawn." However, you are then falling into a linguistic trap, just like someone from the US does not have the same number of words for snow as an Eskimo. The Eskimo has the vocabulary to see the "truth" about the different types of snow, whilst the Westerner just sees "snow". Similarly, when we say a square is either weak or not, we are falling into the same linguistic trap of not seeing the truth. Squares have a range of strength, from weak to not so weak, to strong, to very strong.

Let me give an example. Consider e4, with pawns on d3 and f3. That square is going to be stronger (less weak) than one which is only supported by d3. Then factor in all the pieces defending that square, and you have a monster strong square!

I would be interested if you agree with the above, that the official definition of weak is just a binary "weak or not" distinction, altogether different from reality where things are a lot more granular.