What is a backward pawn?

[Lyudmil Tsvetkov]

See this: http://talkchess.com/forum/viewtopic.ph ... 44&t=52300

[d]4r3/3q3k/pBn1r1pp/Pp1p1p2/2pP1P1P/2P1PP2/3Q1K2/4R2R w - - 0 1
Is not b5 a backward pawn?

This a very instructive position about backward pawns, and no doubt very controversial.

Lyudmil, do you also then consider e3 and g6 pawns as backward? They both have squares in front of them that are defended once but attacked twice -- making them practically "immobile".

Perfect. I would.

But I am afraid Marco will kill me, if I suggest that.

That was the reason I said backward pawns are actually the most frequent pawns, way above passers and other pawns, if you spread the definition wide enough. e3 an g6 perfectly match an extended definition of backward pawns.

I think you raised some interesting points. Whether your definition is strictly correct "by the book" or not, I will not dispute, but I think it makes perfect sense to differentiate between a backward pawn which can be attacked and a backward pawn which is just immobile. Both deserve penalties in different amounts.

Probably, I will do it this way:

-- Define a backward pawn as a pawn that cannot advance "immobile" (based on Lyudmil's definition). Give a small penalty for it (based on rank and file).
-- Further define a weak pawn as any pawn that can be attacked but cannot be dissolved or protected (i.e. Backward pawns on semi-open file, Isolated pawns, overextended pawns, pawns at the base of a chain that is blocked, etc.). Give an additional penalty for such a pawn (based on rank and file)

The benefit here is that we have very clear and strict definitions for static pawn structures and clear bonuses/penalties for them. But, we additionally consider and award bonuses/penalties for dynamic features (can be attacked/can be defended) and we separate them out, just like we do for the threat evaluation of pieces.

I think this is a more elegant approach.

Regards,
Arjun

I think an important thing to consider is that real backward pawns are always not opposed, like b5,e3 and g6 above.

[Lyudmil Tsvetkov]

My take on this is that you are somewhat mixing terms.

A pawn that is defended by a pawn is not considered backward in any book I have (g6 in your first example as it is defended by h7). The fact that it can not safely advance is not so important when it is perfectly safe where it is. If you want to talk about it being immobile, that is a different issue.

the "unopposed" requirement stems from the rook, in the books I have read over the years. A pawn that is backward (can not be safely defended by a friendly pawn) is generally considered to be worse if it is (a) on a half-open file (no enemy pawn in front of it AND (b) the enemy has rooks to attack it.

IMHO, a pawn that is backward and unopposed is not any weaker or stronger than a backward pawn that is opposed, if there are no enemy rooks to contend with. Any backward pawn is weak, and inviting to enemy kings in the endgame. backward pawns on half-open files make inviting targets even in the middle game if you have rooks to attack on the file.

I've seen games decided by two types of backward pawns, repeatedly.

The first is the classic backward pawn on a half-open file, which is just as bad as an isolated pawn on a half-open file, when the enemy has rooks. Pile up on the pawn, tying up the opponent by making him defend, and either win the pawn outright, or switch to some other idea once he is tied down and not coordinated very well.

The second is a pawn that is backward, but the file is not half-open. If you have just one, you might manage to defend it with your king, depending on the position. If you have two, the enemy king can make you commit to saving one and then to eat the other pawn chain. Doesn't matter whether the file is half open or not.

[d]6k1/5p2/4p1p1/3p2P1/1p1P4/p7/P7/6K1 w - - 0 1

I tend to concur with Bob's definition. In the diagram above the e6 pawn is still defended, and thus not vulnerable to direct attack, so that's an argument against calling it backward.

However, since it cannot safely advance, there is an element of backwardness about it, and the square in front of it (e5) can serve as a good outpost for White pieces. These considerations should justify some sort of a penalty for such a pawn, but a lesser one that a fully backward [undefendable by a fellow pawn] pawn on an open file.

The Black b-pawn, even though backward, could be pushed in some cases creating a dangerous advanced passed pawn. It's not as clear whether a backward pawn that sits in the opponent's half of the board deserves any significant penalty.

CL

Carl, whether e6 is defended or not is another matter, completely unrelated to backwardness, i.e. underdevelopedness, inability to advance. Defended and undefended pawns already get their separate bonus/penalty points. We are taling here about the inherent inability of the e6 pawn to advance. That matters very much, pawns are there to advance, help in the attack, promote, etc. If your pawns do not advance to attack the enemy and promote, then it will be your opponent's pawns which will do that to win the game. So that a passive state of inability to advance should always be penalised, regardless of whether such pawns are defended or not. The defended/undefended bonus/penalty is just a small fraction of the penalty for a backward pawn unable to advance without being lost, so that backwardness is the much more important concept.

[d]6k1/5p2/4p1p1/n2p2P1/1p1P4/p7/P7/2N3K1 w - - 0 1
You see above that in the usual case with pieces present, b4 does not represent any real danger of supporting promotion, but is still unable to advance without being lost. So that it is still backward. Of course, a backward pawn on the 4th rank deserves a very small penalty, much less than a backward on the 5th. That is what we have been talking about, the introduction of a unified concept that works across ranks, i.e. a good practical eval term.

How practical and good are current backward definitions that mix backward with weak, isolated, overextended, undefended?

Again, I think the definition I specified, with some 30cps penalty for the 7th rank, 15cps for the 6th rank, 8cps for the 5th rank, and 4cps for the 4th rank, is a good, working definition, unified and applicable across ranks. When you apply a unified feature across ranks, chances are you will get the most out of it.

I ask myself again, who is to blame when modern top engines fully misunderstand backward pawns? And if they badly misplay such pawns, is it possible that the definitions used for backward are good and working ones? Why should you mix backward with isolated, overextended (meaning vertically isolated) and undefended? You already have definitions and penalties for isolated and undefended. No, the only conclusion I draw from that is that currently a complete chaos reigns in the computer chess world as to what actually a backward pawn is. And that is the main reason why engines play so weak with backward pawns.

I wonder who will be the first author who will drastically change his approach and definitions of backward pawns to easily gain (after tuning of course) another 50 elo strength?

I don't think the term "backward" is related to mobility directly. A backward pawn is one that can not be defended, and which is weak where it stands offering the opponent a clear target. There is, to me, a difference between being immobile, and being backward. Immobile is certainly a problem, but not nearly the same as being backward AND immobile.

See this: http://talkchess.com/forum/viewtopic.ph ... 44&t=52300

[d]4r3/3q3k/pBn1r1pp/Pp1p1p2/2pP1P1P/2P1PP2/3Q1K2/4R2R w - - 0 1
Is not b5 a backward pawn?

By the definition I got from Kmoch many years ago, no. It is not attackable as it stands. I can pile up every piece I have on that pawn and all I am threatening to do is sacrifice material. The pawn is definitely immobile, but that can be temporary if I can support the advance square enough times. The thing that makes an isolated pawn weak (it is not and can't be defended by a friendly pawn, which means when it is attacked it has to be defended by a piece) is the same thing that makes a backward pawn weak. Each enemy attack requires a piece to avoid losing the pawn.

Backward pawns generally fall in a discussion about "weak pawns." I'm not sure that fits the b5 pawn above for the reasons I gave. Yes, the pawn should receive a penalty due to lack of mobility, or else the other pawns that are free to move should get a bonus for being able to advance, but calling it weak? What if the most advanced pawn in a chain can't move. Is it really weak? Black pawn on d5 in your position, for example.

There's nothing wrong with disagreeing on this. I am simply giving you my "take" on the topic. In trying to recognize/valuate weaknesses, whether those weaknesses are specific pawns or just weak squares, I am trying to recognize things that will require some action on my part, such as moving a piece to defend the weakness. If the "weakness" doesn't require any attention, then it is not much of a weakness since it doesn't divert my attention from something else.

d5 is not the most advanced pawn of a chain, c4 is. d5 is the base pawn of the d5-c4 chain and as such undefended by definition. It should get a penalty, of course, for being undefended by other pawns, but that is just a fraction of the penalty a real backward pawn would receive.

b5 is not only weak in the sense that it is immobile, there is really much more to it: the essence of it all is that 1 white pawn, c3, stops 2 enemy black pawns, b5 and c4, at the same time. This is an enormous resource efficiency that frees up material/pawn resources for other sections of the board. In some cases it will secure a passer, candidate etc., but this is not a general rule, and it might just secure some resources in terms of initiative, space, attacking chances, tempo play, drawing opportunities, etc. So that it is very necessary to evaluate precisely such pawns.

Apart from that, the penalty for a standard backward pawn in the sense of 1 pawn holding 2 enemy pawns is much bigger than for other weak pawns (undefended, mobile, but unable to advance because of being lost, while opposed, overextended or vertically isolated) apart from (horizontally) isolated pawns. If you give an undefended pawn 10cps penalty, a real backward pawn on the 7th rank would be worth somewhere 40cps or more in the middlegame. Then 6th rank would decrease to 20, 5th to 10, 4th just 5 maybe. But in the general case a real backward pawn is a much more serious deficiency than other weak pawns.

[BeyondCritics]

My take on this is that you are somewhat mixing terms.

A pawn that is defended by a pawn is not considered backward in any book I have (g6 in your first example as it is defended by h7). The fact that it can not safely advance is not so important when it is perfectly safe where it is. If you want to talk about it being immobile, that is a different issue.

the "unopposed" requirement stems from the rook, in the books I have read over the years. A pawn that is backward (can not be safely defended by a friendly pawn) is generally considered to be worse if it is (a) on a half-open file (no enemy pawn in front of it AND (b) the enemy has rooks to attack it.

IMHO, a pawn that is backward and unopposed is not any weaker or stronger than a backward pawn that is opposed, if there are no enemy rooks to contend with. Any backward pawn is weak, and inviting to enemy kings in the endgame. backward pawns on half-open files make inviting targets even in the middle game if you have rooks to attack on the file.

I've seen games decided by two types of backward pawns, repeatedly.

The first is the classic backward pawn on a half-open file, which is just as bad as an isolated pawn on a half-open file, when the enemy has rooks. Pile up on the pawn, tying up the opponent by making him defend, and either win the pawn outright, or switch to some other idea once he is tied down and not coordinated very well.

The second is a pawn that is backward, but the file is not half-open. If you have just one, you might manage to defend it with your king, depending on the position. If you have two, the enemy king can make you commit to saving one and then to eat the other pawn chain. Doesn't matter whether the file is half open or not.

[d]6k1/5p2/4p1p1/3p2P1/1p1P4/p7/P7/6K1 w - - 0 1

I tend to concur with Bob's definition. In the diagram above the e6 pawn is still defended, and thus not vulnerable to direct attack, so that's an argument against calling it backward.

However, since it cannot safely advance, there is an element of backwardness about it, and the square in front of it (e5) can serve as a good outpost for White pieces. These considerations should justify some sort of a penalty for such a pawn, but a lesser one that a fully backward [undefendable by a fellow pawn] pawn on an open file.

The Black b-pawn, even though backward, could be pushed in some cases creating a dangerous advanced passed pawn. It's not as clear whether a backward pawn that sits in the opponent's half of the board deserves any significant penalty.

CL

Crafty calls that a3 pawn a "hidden passed pawn". GM Dzhindi used to call this a protected passed pawn himself, because a3 is certainly passed here when you think about it and it is defended by b4. after b3 black ends up with a passed pawn for certain.

You really do not read this thread.

When you add pieces, there is no danger of a passed pawn.

[d][d]6k1/5p2/4p1p1/n2p2P1/1p1P4/p7/P7/2N3K1 w - - 0 1
One knight each side added; where is the danger of the hidden passed a3 pawn?
a3 is not an immediate danger, but b4 is certainly backward, like it or not, a2 stops both a3 and b4 pawns by blocking a3 and attacking the stop square of b4.

Very simple. White has to avoid any move that lets me force the exchange of knights. Because allowing such is an instant loss. Unless white chooses to brink his king over to the a-file area, which ties it down and restricts white's ability to defend elsewhere.

Adding the knights does NOT eliminate the advantage of a3-b4, it just makes it harder to use that advantage. In this case, as black I would try to get the knight to c3 and take on a2. White knight will have great trouble with the a/b pawns after that

We are talking here about a static feature, and the static feature is that one white pawn, a2, holds 2 black pawns, a3 and b4, simultaneously.

He simply told you, that crafty recognizes the danger in this pawn setup. b4 is "backward" and a "hidden passed pawn" at the same time. What is wrong with that? At some time the "backwardness" tells, at some time the "hidden passed pawn"ness tells, both extremly dangerous. A succesfull breakthrough is even more dangerous than the danger of loosing a pawn, since it wins on the spot.

[BeyondCritics]

What about b7?

[d]7k/1p6/p1p5/P7/1P6/8/8/7K w - - 0 1

[Lyudmil Tsvetkov]

My take on this is that you are somewhat mixing terms.

A pawn that is defended by a pawn is not considered backward in any book I have (g6 in your first example as it is defended by h7). The fact that it can not safely advance is not so important when it is perfectly safe where it is. If you want to talk about it being immobile, that is a different issue.

the "unopposed" requirement stems from the rook, in the books I have read over the years. A pawn that is backward (can not be safely defended by a friendly pawn) is generally considered to be worse if it is (a) on a half-open file (no enemy pawn in front of it AND (b) the enemy has rooks to attack it.

IMHO, a pawn that is backward and unopposed is not any weaker or stronger than a backward pawn that is opposed, if there are no enemy rooks to contend with. Any backward pawn is weak, and inviting to enemy kings in the endgame. backward pawns on half-open files make inviting targets even in the middle game if you have rooks to attack on the file.

I've seen games decided by two types of backward pawns, repeatedly.

The first is the classic backward pawn on a half-open file, which is just as bad as an isolated pawn on a half-open file, when the enemy has rooks. Pile up on the pawn, tying up the opponent by making him defend, and either win the pawn outright, or switch to some other idea once he is tied down and not coordinated very well.

The second is a pawn that is backward, but the file is not half-open. If you have just one, you might manage to defend it with your king, depending on the position. If you have two, the enemy king can make you commit to saving one and then to eat the other pawn chain. Doesn't matter whether the file is half open or not.

[d]6k1/5p2/4p1p1/3p2P1/1p1P4/p7/P7/6K1 w - - 0 1

I tend to concur with Bob's definition. In the diagram above the e6 pawn is still defended, and thus not vulnerable to direct attack, so that's an argument against calling it backward.

However, since it cannot safely advance, there is an element of backwardness about it, and the square in front of it (e5) can serve as a good outpost for White pieces. These considerations should justify some sort of a penalty for such a pawn, but a lesser one that a fully backward [undefendable by a fellow pawn] pawn on an open file.

The Black b-pawn, even though backward, could be pushed in some cases creating a dangerous advanced passed pawn. It's not as clear whether a backward pawn that sits in the opponent's half of the board deserves any significant penalty.

CL

Crafty calls that a3 pawn a "hidden passed pawn". GM Dzhindi used to call this a protected passed pawn himself, because a3 is certainly passed here when you think about it and it is defended by b4. after b3 black ends up with a passed pawn for certain.

You really do not read this thread.

When you add pieces, there is no danger of a passed pawn.

[d][d]6k1/5p2/4p1p1/n2p2P1/1p1P4/p7/P7/2N3K1 w - - 0 1
One knight each side added; where is the danger of the hidden passed a3 pawn?
a3 is not an immediate danger, but b4 is certainly backward, like it or not, a2 stops both a3 and b4 pawns by blocking a3 and attacking the stop square of b4.

Very simple. White has to avoid any move that lets me force the exchange of knights. Because allowing such is an instant loss. Unless white chooses to brink his king over to the a-file area, which ties it down and restricts white's ability to defend elsewhere.

Adding the knights does NOT eliminate the advantage of a3-b4, it just makes it harder to use that advantage. In this case, as black I would try to get the knight to c3 and take on a2. White knight will have great trouble with the a/b pawns after that

We are talking here about a static feature, and the static feature is that one white pawn, a2, holds 2 black pawns, a3 and b4, simultaneously.

He simply told you, that crafty recognizes the danger in this pawn setup. b4 is "backward" and a "hidden passed pawn" at the same time. What is wrong with that? At some time the "backwardness" tells, at some time the "hidden passed pawn"ness tells, both extremly dangerous. A succesfull breakthrough is even more dangerous than the danger of loosing a pawn, since it wins on the spot.

b4 is backward and a3 is a hidden passed pawn, but there is a difference and it is major.

While the concept of backwardness works in all situations with or without pieces on the board, the concept of hidden pased pawn works exclusively in a pure pawn setting. I thought programmers were in general against ad-hoc rules. Is not that an ad-hoc rule which is valid only for a limited specific setting?

I think that a3 should already get its very nice bonus for its advanced location in psqt.

[Lyudmil Tsvetkov]

What about b7?

[d]7k/1p6/p1p5/P7/1P6/8/8/7K w - - 0 1

I hope this is not a position, but just an illustration.

Well, 2 white pawns hold 3 black ones, so there must be a backward pawn among the black pawns. As a backward pawn supposedly should be a pawn that is not opposed, I think that the black backward pawn is c6.

c6 is a defended, chain pawn, but it is still backward. The reason is that the only frinedly pawn behind on adjacent files, b7, is unable to support the advance of c6 as it is unable to advance itself. One must be very careful with definitions. So in the case of a chain pawn, it would qualify for backward, if the only pawn behind on adjacent files that could support its advance, is also unable to advance without being lost, although being opposed, or blocked, would be the right definition.

I would not consider myself b7 as backward, as it is opposed. But of course, it deserves some penalty for still being on the initial 7th rank, but that is not closely related to backwardness, apart from wording. Leaving a hole/weak spot/undefended square on b6 on the 3rd rank is another matter.

Please do not ask me about what pawn b4 is, as its stop square is controlled by 2 enemy pawns and no friendly pawns could support its advance.

[Lyudmil Tsvetkov]

What about b7?

[d]7k/1p6/p1p5/P7/1P6/8/8/7K w - - 0 1

I hope this is not a position, but just an illustration.

Well, 2 white pawns hold 3 black ones, so there must be a backward pawn among the black pawns. As a backward pawn supposedly should be a pawn that is not opposed, I think that the black backward pawn is c6.

c6 is a defended, chain pawn, but it is still backward. The reason is that the only frinedly pawn behind on adjacent files, b7, is unable to support the advance of c6 as it is unable to advance itself. One must be very careful with definitions. So in the case of a chain pawn, it would qualify for backward, if the only pawn behind on adjacent files that could support its advance, is also unable to advance without being lost, although being opposed, or blocked, would be the right definition.

I would not consider myself b7 as backward, as it is opposed. But of course, it deserves some penalty for still being on the initial 7th rank, but that is not closely related to backwardness, apart from wording. Leaving a hole/weak spot/undefended square on b6 on the 3rd rank is another matter.

Please do not ask me about what pawn b4 is, as its stop square is controlled by 2 enemy pawns and no friendly pawns could support its advance.

When I look at the above diagram now, I remember that SF at some point tested, even with CLOP, the special penalty for a pawn whose stop square is controlled by 2 enemy pawns and no friendly pawns being able to support its advance from behind. Of course, it did not succeed, and the value suggested by CLOP was ridiculously small. Well, they should have added just one more condition to the definition of the pawn: that this pawn should not be opposed.

[d]6k1/8/p1p5/P1P5/1P6/8/8/6K1 w - - 0 1
b4 above deserves an enormous penalty, 1.5 times bigger than normal backward pawns, as it is unable to advance without being lost even with the help of pieces. I call such pawns backward-fated, as their fate is to remain backward. In sharp distinction to normal backward pawns, that could still advance with the help of friendly pieces, backward-fated pawns can not do so under any condition. Hence the need for an increased penalty.

SF tried this, but I guess they simply forgot to specify that such a pawn as b4 above should be necessarily not opposed.

Please do not tell me that a5 and c5 are both hidden passers and that b4-b5 wins on the spot, as this is just an illustration and with pieces on the board there is no winning move for white, while the extremely serious deficiency of b4 remains.

[bob]

My take on this is that you are somewhat mixing terms.

A pawn that is defended by a pawn is not considered backward in any book I have (g6 in your first example as it is defended by h7). The fact that it can not safely advance is not so important when it is perfectly safe where it is. If you want to talk about it being immobile, that is a different issue.

the "unopposed" requirement stems from the rook, in the books I have read over the years. A pawn that is backward (can not be safely defended by a friendly pawn) is generally considered to be worse if it is (a) on a half-open file (no enemy pawn in front of it AND (b) the enemy has rooks to attack it.

IMHO, a pawn that is backward and unopposed is not any weaker or stronger than a backward pawn that is opposed, if there are no enemy rooks to contend with. Any backward pawn is weak, and inviting to enemy kings in the endgame. backward pawns on half-open files make inviting targets even in the middle game if you have rooks to attack on the file.

I've seen games decided by two types of backward pawns, repeatedly.

The first is the classic backward pawn on a half-open file, which is just as bad as an isolated pawn on a half-open file, when the enemy has rooks. Pile up on the pawn, tying up the opponent by making him defend, and either win the pawn outright, or switch to some other idea once he is tied down and not coordinated very well.

The second is a pawn that is backward, but the file is not half-open. If you have just one, you might manage to defend it with your king, depending on the position. If you have two, the enemy king can make you commit to saving one and then to eat the other pawn chain. Doesn't matter whether the file is half open or not.

[d]6k1/5p2/4p1p1/3p2P1/1p1P4/p7/P7/6K1 w - - 0 1

I tend to concur with Bob's definition. In the diagram above the e6 pawn is still defended, and thus not vulnerable to direct attack, so that's an argument against calling it backward.

However, since it cannot safely advance, there is an element of backwardness about it, and the square in front of it (e5) can serve as a good outpost for White pieces. These considerations should justify some sort of a penalty for such a pawn, but a lesser one that a fully backward [undefendable by a fellow pawn] pawn on an open file.

The Black b-pawn, even though backward, could be pushed in some cases creating a dangerous advanced passed pawn. It's not as clear whether a backward pawn that sits in the opponent's half of the board deserves any significant penalty.

CL

Carl, whether e6 is defended or not is another matter, completely unrelated to backwardness, i.e. underdevelopedness, inability to advance. Defended and undefended pawns already get their separate bonus/penalty points. We are taling here about the inherent inability of the e6 pawn to advance. That matters very much, pawns are there to advance, help in the attack, promote, etc. If your pawns do not advance to attack the enemy and promote, then it will be your opponent's pawns which will do that to win the game. So that a passive state of inability to advance should always be penalised, regardless of whether such pawns are defended or not. The defended/undefended bonus/penalty is just a small fraction of the penalty for a backward pawn unable to advance without being lost, so that backwardness is the much more important concept.

[d]6k1/5p2/4p1p1/n2p2P1/1p1P4/p7/P7/2N3K1 w - - 0 1
You see above that in the usual case with pieces present, b4 does not represent any real danger of supporting promotion, but is still unable to advance without being lost. So that it is still backward. Of course, a backward pawn on the 4th rank deserves a very small penalty, much less than a backward on the 5th. That is what we have been talking about, the introduction of a unified concept that works across ranks, i.e. a good practical eval term.

How practical and good are current backward definitions that mix backward with weak, isolated, overextended, undefended?

Again, I think the definition I specified, with some 30cps penalty for the 7th rank, 15cps for the 6th rank, 8cps for the 5th rank, and 4cps for the 4th rank, is a good, working definition, unified and applicable across ranks. When you apply a unified feature across ranks, chances are you will get the most out of it.

I ask myself again, who is to blame when modern top engines fully misunderstand backward pawns? And if they badly misplay such pawns, is it possible that the definitions used for backward are good and working ones? Why should you mix backward with isolated, overextended (meaning vertically isolated) and undefended? You already have definitions and penalties for isolated and undefended. No, the only conclusion I draw from that is that currently a complete chaos reigns in the computer chess world as to what actually a backward pawn is. And that is the main reason why engines play so weak with backward pawns.

I wonder who will be the first author who will drastically change his approach and definitions of backward pawns to easily gain (after tuning of course) another 50 elo strength?

I don't think the term "backward" is related to mobility directly. A backward pawn is one that can not be defended, and which is weak where it stands offering the opponent a clear target. There is, to me, a difference between being immobile, and being backward. Immobile is certainly a problem, but not nearly the same as being backward AND immobile.

See this: http://talkchess.com/forum/viewtopic.ph ... 44&t=52300

[d]4r3/3q3k/pBn1r1pp/Pp1p1p2/2pP1P1P/2P1PP2/3Q1K2/4R2R w - - 0 1
Is not b5 a backward pawn?

By the definition I got from Kmoch many years ago, no. It is not attackable as it stands. I can pile up every piece I have on that pawn and all I am threatening to do is sacrifice material. The pawn is definitely immobile, but that can be temporary if I can support the advance square enough times. The thing that makes an isolated pawn weak (it is not and can't be defended by a friendly pawn, which means when it is attacked it has to be defended by a piece) is the same thing that makes a backward pawn weak. Each enemy attack requires a piece to avoid losing the pawn.

Backward pawns generally fall in a discussion about "weak pawns." I'm not sure that fits the b5 pawn above for the reasons I gave. Yes, the pawn should receive a penalty due to lack of mobility, or else the other pawns that are free to move should get a bonus for being able to advance, but calling it weak? What if the most advanced pawn in a chain can't move. Is it really weak? Black pawn on d5 in your position, for example.

There's nothing wrong with disagreeing on this. I am simply giving you my "take" on the topic. In trying to recognize/valuate weaknesses, whether those weaknesses are specific pawns or just weak squares, I am trying to recognize things that will require some action on my part, such as moving a piece to defend the weakness. If the "weakness" doesn't require any attention, then it is not much of a weakness since it doesn't divert my attention from something else.

d5 is not the most advanced pawn of a chain, c4 is. d5 is the base pawn of the d5-c4 chain and as such undefended by definition. It should get a penalty, of course, for being undefended by other pawns, but that is just a fraction of the penalty a real backward pawn would receive.

b5 is not only weak in the sense that it is immobile, there is really much more to it: the essence of it all is that 1 white pawn, c3, stops 2 enemy black pawns, b5 and c4, at the same time. This is an enormous resource efficiency that frees up material/pawn resources for other sections of the board. In some cases it will secure a passer, candidate etc., but this is not a general rule, and it might just secure some resources in terms of initiative, space, attacking chances, tempo play, drawing opportunities, etc. So that it is very necessary to evaluate precisely such pawns.

Apart from that, the penalty for a standard backward pawn in the sense of 1 pawn holding 2 enemy pawns is much bigger than for other weak pawns (undefended, mobile, but unable to advance because of being lost, while opposed, overextended or vertically isolated) apart from (horizontally) isolated pawns. If you give an undefended pawn 10cps penalty, a real backward pawn on the 7th rank would be worth somewhere 40cps or more in the middlegame. Then 6th rank would decrease to 20, 5th to 10, 4th just 5 maybe. But in the general case a real backward pawn is a much more serious deficiency than other weak pawns.

This is about "degrees" of weakness. Because things can change. An isolated pawn is almost guaranteed to stay isolated unless the other side voluntarily makes a capture that lets the isolated pawn move over a file and become not isolated.

A backward pawn is really bad when you have something like c4-d3 while black has c5-e5. The d3 pawn is not moving, period, no matter how many pieces white brings over. At least not until either c5 or e5 is eliminated. But that is very difficult.

The example you quote with c4-d3 with black on c5 certainly makes d3 difficult to advance, but all white needs is one more piece than black and that issue vanished.

As we go down the above list, the advantage is less significant and less permanent. One has to be careful about evaluating such pawns and giving a significant penalty for a fleeting advantage. Chances are to create such a pawn for the opponent, you have to give up something yourself. You probably would not want to trade something real like a bishop pair advantage to create that last example of a backward pawn, as that kind of weakness is much easier to liquidate than one that is more permanent.

A volatile evaluation (one that bounces all over the place, changing quickly and dramatically) can easily be worse than no evaluation at all.

[bob]

My take on this is that you are somewhat mixing terms.

A pawn that is defended by a pawn is not considered backward in any book I have (g6 in your first example as it is defended by h7). The fact that it can not safely advance is not so important when it is perfectly safe where it is. If you want to talk about it being immobile, that is a different issue.

the "unopposed" requirement stems from the rook, in the books I have read over the years. A pawn that is backward (can not be safely defended by a friendly pawn) is generally considered to be worse if it is (a) on a half-open file (no enemy pawn in front of it AND (b) the enemy has rooks to attack it.

IMHO, a pawn that is backward and unopposed is not any weaker or stronger than a backward pawn that is opposed, if there are no enemy rooks to contend with. Any backward pawn is weak, and inviting to enemy kings in the endgame. backward pawns on half-open files make inviting targets even in the middle game if you have rooks to attack on the file.

I've seen games decided by two types of backward pawns, repeatedly.

The first is the classic backward pawn on a half-open file, which is just as bad as an isolated pawn on a half-open file, when the enemy has rooks. Pile up on the pawn, tying up the opponent by making him defend, and either win the pawn outright, or switch to some other idea once he is tied down and not coordinated very well.

The second is a pawn that is backward, but the file is not half-open. If you have just one, you might manage to defend it with your king, depending on the position. If you have two, the enemy king can make you commit to saving one and then to eat the other pawn chain. Doesn't matter whether the file is half open or not.

[d]6k1/5p2/4p1p1/3p2P1/1p1P4/p7/P7/6K1 w - - 0 1

I tend to concur with Bob's definition. In the diagram above the e6 pawn is still defended, and thus not vulnerable to direct attack, so that's an argument against calling it backward.

However, since it cannot safely advance, there is an element of backwardness about it, and the square in front of it (e5) can serve as a good outpost for White pieces. These considerations should justify some sort of a penalty for such a pawn, but a lesser one that a fully backward [undefendable by a fellow pawn] pawn on an open file.

The Black b-pawn, even though backward, could be pushed in some cases creating a dangerous advanced passed pawn. It's not as clear whether a backward pawn that sits in the opponent's half of the board deserves any significant penalty.

CL

Crafty calls that a3 pawn a "hidden passed pawn". GM Dzhindi used to call this a protected passed pawn himself, because a3 is certainly passed here when you think about it and it is defended by b4. after b3 black ends up with a passed pawn for certain.

You really do not read this thread.

When you add pieces, there is no danger of a passed pawn.

[d][d]6k1/5p2/4p1p1/n2p2P1/1p1P4/p7/P7/2N3K1 w - - 0 1
One knight each side added; where is the danger of the hidden passed a3 pawn?
a3 is not an immediate danger, but b4 is certainly backward, like it or not, a2 stops both a3 and b4 pawns by blocking a3 and attacking the stop square of b4.

Very simple. White has to avoid any move that lets me force the exchange of knights. Because allowing such is an instant loss. Unless white chooses to brink his king over to the a-file area, which ties it down and restricts white's ability to defend elsewhere.

Adding the knights does NOT eliminate the advantage of a3-b4, it just makes it harder to use that advantage. In this case, as black I would try to get the knight to c3 and take on a2. White knight will have great trouble with the a/b pawns after that

We are talking here about a static feature, and the static feature is that one white pawn, a2, holds 2 black pawns, a3 and b4, simultaneously.

Sorry, but you can't have it BOTH ways.

remove the knights.

Is b4 weak, or is a3 overwhelmingly strong? a3 is very strong so long as black can get enough pieces to attack b3 to make pushing b3 safe. That's not "static" at all, that is dynamic. So leave the pieces out of it. b4 is weak, as it can't safely advance, but there is a stinger in that b4 CAN advance because a3 will promote before white's pawn that takes on b3. In this position, the white pawn on a3 is not really holding back anything whatsoever. And, in fact, my program considers this a significant pawn advantage, not a weakness. Why? Ask GM Dzhindi. We had that discussion almost 20 years ago and he convinced me it is correct. Yes, Crafty still gets a penalty for b4 being weak, but it gets a significantly larger bonus for a3 being so strong.

[Lyudmil Tsvetkov]

[d]6k1/8/p1p5/P1P5/1P6/8/8/6K1 w - - 0 1

How could we define b4 above?

Well, it seems simple. A backward-fated pawn would be a pawn that:

- is not opposed
- whose stop square is controlled by 2 enemy pawns
- and both of which enemy pawns are blocked by friendly pawns
- and there are no other friendly pawns on the same rank or behind on adjacent files

4 necessary conditions, a condition less simply will not do.

I would assign backward-fated pawns some 50cps penalty, way above the 30cps penalty for a normal backward pawn. And would not count ranks, as those pawns are very specific. It should be mentioned also that just adding the penalties for 2 normal backward pawns would not quite do it, as there is a quantitative difference.

If SF or some other engine applied the definition correctly, they would see it really makes sense to introduce such a peculiar pawn term. If engines do not understand backward pawns, they are fully clueless of backward-fated ones.

People have been laughing at me every time I mentioned backward-fated pawns, but do not you see they are real?