user18390: I made a horrible decision as black in a game, and I do not understand why it's incorrect.
[fen "rn2kb1r/pp2pppp/1q3n2/2pp4/3P1P2/2PQPN2/PP4PP/RNB1K2R b - - 0 1"]

I played c4, Stockfish considers the position to be + 0.4 after the move. My reasoning: I forever block white's bad bishop behind his blocked pawns, while keeping my good bishop. Since I gain a tempo on the queen, I can move my queen right away to be able to answer the break b3 with b5. 
I am also thinking that my position is much better, as white has a hole on e4 and I don't have such a weakness, so I thought I'd capitalize on my advantage by closing up the position. 
Stockfish considers this move to be a really poor move, e6 leading to an evaluation of -0.7. 
I've had this several time, and it's unclear to me why my move is bad, even though it gives me an inferior position from a superior one.
Is it always bad to close up the position this way, or is it specific to the position ? Why is it bad, because I forever lose my main pawn break ? Or because my "good bishop" has no target and is therefore not really good ? 

user19877: It is slow. At a time you should be developing and getting the rest of your pieces out, you play c4, meaning that eventually to get your standard play with b5-b4, you will need to finish your development, then move your queen again, and only then get in b5-b4. That gives time for white to do a lot of different things, depending on how you develop. You will also have to take the time to play Ne4 almost immediately so you can play f5 since if white gets in e4 first, that is also going to be super advantageous to him.
It is a common mistake to change the base of the pawn structure in the opening, slowing one's play.

user12873: ...c4 is generally bad because it releases the tension on White's d4-pawn. This makes it much easier for White to get away with pushing e4, since the e3-pawn doesn't need to support the d4-pawn anymore.
You're correct that White does have a weak hole on e4, but after playing Qc2 and Nbd2, he's ready to push e4 and gain a central initiative.

user18367: The other answers were great, but I think you could sum it up like this :
the player who has built the stonewall is looking for a locked center so that he can benefit from the time to build up an attack on your king, funneling his pieces over in the vicinity of your king without having to worry about central counter-play.
Doing c4 might superficially look like gaining space, but it really helps the opponent in keeping the center locked, by giving up a possible break which might be needed.

user924: Some points:
White's "bad" bishop is already locked behind their pawns, your move doesn't change that, it's a feature of the opening white is playing. Long term white could go for Bc1-d2-e1-h4, or play b3 and Ba3. In fact in your proposed line of 1...c4 Qc2 2.Qc6 3.b3 b5, white has 4.Ba3. Note that if you don't play ...c4, Ba3 sometimes fails to ...cxd4 cxd4 Bxa3 Nxa3 Qa5+ picking up the knight, but if you play ...c4 white doesn't have to think about that possibility.
 [title "4.Ba3"]
 [fen "rn2kb1r/pp2pppp/1q3n2/2pp4/3P1P2/2PQPN2/PP4PP/RNB1K2R b - - 0 1"]

 1...c4 2.Qc2 Qc6 3.b3 b5 4.Ba3

Similarly, your "good" bishop is already good. But it doesn't gain much from ...c4.
You have a good square on e4, but if you put a knight there then white will exchange it for his and there will be a pawn on that square. If white plays Ne5 and you exchange it, they can take fxe5 and get an attack over the f-file.
You removed the tension (white doesn't have to care about the option ...cxd4 anymore) and now have few good pawn breaks (I don't think ...f6 and ...e5 is going to work soon). If one the other hand white manages e3-e4, then your pawn on c4 may become weak. Or white can attack it with b3 and a4. Or go for a kingside attack with g2-g4.
So I don't see your points. That said, 0.7 is more of an advantage than I had expected, maybe there is a way for them to force you to waste some more time, or win a pawn?

user13433: First of all, your plan of keeping White's queenside blocked doesn't quite work out in any case: After e.g. 1...c4 2. Qe2 Qc7 3. b3 b5 White can simply continue attacking your pawn chain by 4. a4 and you cannot answer 4...a6 because of 5. axb5 axb5? 6. Rxa8. 
If you try to protect the rook by 2...Qc6, White can insert 3. Ne5 to displace the queen. 
But even if White does not play a4, there are some things to note:

The blockade is not complete anyways, as the Bc1 can always escape
its own pawn chain via a3.
The move 1...c4 is very committal, 1...e6
on the other hand keeps all options open and even adds some more by
supporting the development of your kingside. Crucially, you can now
answer dxc5 by Bxc5, and since e3 would become super weak,
White is discouraged to take on c5 anytime soon. The option of
playing ...c4 thus won't disappear after 1...e6!
But in the meantime, the pawn keeps up pressure on the White centre from c5, pressure that an immediate ...c4 loses.
In this light, you'd like your queen to stay on b6, too, where she eyes
both the g1-a7 diagonal as well as b2.


user3594: Good question! The positional priorities in this position do not really lie in whose bishop has more prospects, but rather in the emerging pawn structure, potential pawn breaks, and either side's ability to create targets and holes in opponent's camp. 
In short, c4 here is an extremely committal move which should only be played if it can be backed by very strong concrete ideas, which do not exist in this position. Why does the fact that it's committal makes it into a poor choice? It's simply because it resolves white's strategy into something immediate and concrete, namely: to undermine black's pawn chain and create a weak pawn out of c4, and to this end, the almost immediate e4 pawn break is perfectly playable for white without any drawbacks and black has nearly no means of preventing it. So in hindsight, moves such as c4 and similar ones in analogous positions, are only good if you are sure you can stop your opponent's relevant pawn breaks. Otherwise you're creating overly advanced pawns that will eventually turn into weaknesses that you cannot easily parry. 
Remember, a pawn is considered to be weak if (all 3 must be met simultaneously):

it cannot move
it is isolated (not defensible by pawns)
it can be attacked. 

To summarise: with the unavoidable e4 by white and a4 in reply to b5, the c4 pawn is bound to become a weakness as it meets all 3 said conditions. 
Gained tempi and temporarily blocked out bishops are secondary in such positions, unless you have an actual threat following your pawn push (such as, an imminent knight jump to d3!)
More concretely, let's take a look at a few possible continuations as illustrated in the following diagrams:
Left: Early e4 by white  |  mid: early b5 attempt  |  right: e4 blockade attempt




Left: Immediately undermining c4's defense after Qe2, Nbd2, if black takes, c4 is dropping soon and both knights will be well established centrally. And if black tries to sit still, e4-e5 is a threat, leaving black's kingside heavily undefended and white's pawn push is quite straightforward, black will lack space and the ability to create a counter-attack.
Mid: Black prepares for the immediate b5 (with Qc7) in order to reinforce c4 which leads to: Qe2, Qc7, Nbd2, e6, e4, b5, f5! and soon followed by a4. Notice how white's perfectly undermining the entire pawn backbone (e6, d5, b5) of c4.
Right: Black simply tries to stop e4 by blockading it with a knight, but since it cannot really be followed up by f5 (as shown in the diagram), it will easily be challenged with Nbd2 after which black either has to take on d2 which revives e4 again, or lets white take on e4 leaving a ton of light square weaknesses behind along with a permanent knight post on e5. Note that in this structure, black has no prospect for ever landing a knight on d3, leaving the light square control that the overly advanced pawns have secured virtually unusable. Finally, notice that in neither of these cases, black's left with any form of initiative or targets in white's structure to allow for any counter-attack. 

Lastly, by not playing c4, you can still entertain a timely resolution of the central pawns in order to either simplify or create weak points in white's centre. And to connect with our discussions, by holding still with the pawn on c5 you are actually stopping white's e4 push as after, say, e6, Nbd2, Be7, e4 you can simply take both on e4 and d4 not allowing white any central control (unlike the case of c4 where white always had clear spatial advantage), and your structure is devoid of weaknesses. If anything, white will be the only side with potential dark square weaknesses. And if white recaptures on d4 with the pawn, then it's a comfortable IQP structure with easy play for black.


18390: <p>I made a horrible decision as black in a game, and I do not understand why it's incorrect.</p>

<pre><code>[fen "rn2kb1r/pp2pppp/1q3n2/2pp4/3P1P2/2PQPN2/PP4PP/RNB1K2R b - - 0 1"]
</code></pre>

<p>I played c4, Stockfish considers the position to be + 0.4 after the move. My reasoning: I forever block white's bad bishop behind his blocked pawns, while keeping my good bishop. Since I gain a tempo on the queen, I can move my queen right away to be able to answer the break b3 with b5. </p>

<p>I am also thinking that my position is much better, as white has a hole on e4 and I don't have such a weakness, so I thought I'd capitalize on my advantage by closing up the position. </p>

<p>Stockfish considers this move to be a really poor move, e6 leading to an evaluation of -0.7. </p>

<p>I've had this several time, and it's unclear to me why my move is bad, even though it gives me an inferior position from a superior one.</p>

<p>Is it always bad to close up the position this way, or is it specific to the position ? Why is it bad, because I forever lose my main pawn break ? Or because my "good bishop" has no target and is therefore not really good ? </p>
 19877: <p>It is slow. At a time you should be developing and getting the rest of your pieces out, you play c4, meaning that eventually to get your standard play with b5-b4, you will need to finish your development, then move your queen again, and only then get in b5-b4. That gives time for white to do a lot of different things, depending on how you develop. You will also have to take the time to play Ne4 almost immediately so you can play f5 since if white gets in e4 first, that is also going to be super advantageous to him.</p>

<p>It is a common mistake to change the base of the pawn structure in the opening, slowing one's play.</p>
 12873: <p>...c4 is generally bad because it releases the tension on White's d4-pawn. This makes it much easier for White to get away with pushing e4, since the e3-pawn doesn't need to support the d4-pawn anymore.</p>

<p>You're correct that White does have a weak hole on e4, but after playing Qc2 and Nbd2, he's ready to push e4 and gain a central initiative.</p>
 18367: <p>The other answers were great, but I think you could sum it up like this :
the player who has built the stonewall is looking for a locked center so that he can benefit from the time to build up an attack on your king, funneling his pieces over in the vicinity of your king without having to worry about central counter-play.</p>

<p>Doing c4 might superficially look like gaining space, but it really helps the opponent in keeping the center locked, by giving up a possible break which might be needed.</p>
 924: <p>Some points:</p>

<p>White's "bad" bishop is already locked behind their pawns, your move doesn't change that, it's a feature of the opening white is playing. Long term white could go for <code>Bc1-d2-e1-h4</code>, or play <code>b3</code> and <code>Ba3</code>. In fact in your proposed line of <code>1...c4 Qc2 2.Qc6 3.b3 b5</code>, white has <code>4.Ba3</code>. Note that if you don't play <code>...c4, Ba3</code> sometimes fails to <code>...cxd4 cxd4 Bxa3 Nxa3 Qa5+</code> picking up the knight, but if you play <code>...c4</code> white doesn't have to think about that possibility.</p>

<pre><code> [title "4.Ba3"]
 [fen "rn2kb1r/pp2pppp/1q3n2/2pp4/3P1P2/2PQPN2/PP4PP/RNB1K2R b - - 0 1"]

 1...c4 2.Qc2 Qc6 3.b3 b5 4.Ba3
</code></pre>

<p>Similarly, your "good" bishop is already good. But it doesn't gain much from <code>...c4</code>.</p>

<p>You have a good square on <code>e4</code>, but if you put a knight there then white will exchange it for his and there will be a pawn on that square. If white plays <code>Ne5</code> and you exchange it, they can take <code>fxe5</code> and get an attack over the f-file.</p>

<p>You removed the tension (white doesn't have to care about the option <code>...cxd4</code> anymore) and now have few good pawn breaks (I don't think <code>...f6</code> and <code>...e5</code> is going to work soon). If one the other hand white manages <code>e3-e4</code>, then your pawn on <code>c4</code> may become weak. Or white can attack it with <code>b3</code> and <code>a4</code>. Or go for a kingside attack with <code>g2-g4</code>.</p>

<p>So I don't see your points. That said, <code>0.7</code> is more of an advantage than I had expected, maybe there is a way for them to force you to waste some more time, or win a pawn?</p>
 13433: <p>First of all, your plan of keeping White's queenside blocked doesn't quite work out in any case: After e.g. <strong>1...c4 2. Qe2 Qc7 3. b3 b5</strong> White can simply continue attacking your pawn chain by <strong>4. a4</strong> and you cannot answer <strong>4...a6</strong> because of <strong>5. axb5 axb5? 6. Rxa8</strong>. 
If you try to protect the rook by <strong>2...Qc6</strong>, White can insert <strong>3. Ne5</strong> to displace the queen. </p>

<p>But even if White does not play a4, there are some things to note:</p>

<ul>
<li>The blockade is not complete anyways, as the Bc1 can always escape
its own pawn chain via a3.</li>
<li>The move <strong>1...c4</strong> is very committal, <strong>1...e6</strong>
on the other hand keeps all options open and even adds some more by
supporting the development of your kingside. Crucially, you can now
answer <strong>dxc5</strong> by <strong>Bxc5</strong>, and since e3 would become super weak,
White is discouraged to take on c5 anytime soon. The option of
playing <strong>...c4</strong> thus won't disappear after <strong>1...e6</strong>!</li>
<li>But in the meantime, the pawn keeps up pressure on the White centre from c5, pressure that an immediate <strong>...c4</strong> loses.</li>
<li>In this light, you'd like your queen to stay on b6, too, where she eyes
both the g1-a7 diagonal as well as b2.</li>
</ul>
 3594: <p>Good question! The positional priorities in this position do not really lie in whose bishop has more prospects, but rather in the emerging pawn structure, potential pawn breaks, and either side's ability to create targets and holes in opponent's camp. </p>

<p>In short, <code>c4</code> here is an extremely committal move which should only be played if it can be backed by very strong concrete ideas, which do not exist in this position. Why does the fact that it's committal makes it into a poor choice? It's simply because it resolves white's strategy into something immediate and concrete, namely: to undermine black's pawn chain and create a weak pawn out of <code>c4</code>, and to this end, the almost immediate <code>e4</code> pawn break is perfectly playable for white without any drawbacks and black has nearly no means of preventing it. So in hindsight, moves such as <code>c4</code> and similar ones in analogous positions, are only good if you are sure you can stop your opponent's relevant pawn breaks. Otherwise you're creating overly advanced pawns that will eventually turn into weaknesses that you cannot easily parry. 
Remember, a pawn is considered to be weak if (all 3 must be met simultaneously):</p>

<ul>
<li>it <strong>cannot</strong> move</li>
<li>it is <strong>isolated</strong> (not defensible by pawns)</li>
<li>it <strong>can be</strong> attacked. </li>
</ul>

<p>To summarise: with the unavoidable <code>e4</code> by white and <code>a4</code> in reply to <code>b5</code>, the <code>c4</code> pawn is bound to become a weakness as it meets all 3 said conditions. 
Gained tempi and temporarily blocked out bishops are secondary in such positions, unless you have an actual threat following your pawn push (such as, an imminent knight jump to <code>d3</code>!)</p>

<p>More concretely, let's take a look at a few possible continuations as illustrated in the following diagrams:</p>

<p><strong>Left:</strong> Early <code>e4</code> by white  |  <strong>mid:</strong> early <code>b5</code> attempt  |  <strong>right:</strong> <code>e4</code> blockade attempt</p>

<p><a href="https://i.stack.imgur.com/yEY5Zb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yEY5Zb.png" alt="enter image description here"></a>
<a href="https://i.stack.imgur.com/AKARPb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AKARPb.png" alt="enter image description here"></a>
<a href="https://i.stack.imgur.com/0Lxzab.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0Lxzab.png" alt="enter image description here"></a></p>

<ul>
<li><p>Left: Immediately undermining <code>c4</code>'s defense after <code>Qe2, Nbd2</code>, if black takes, <code>c4</code> is dropping soon and both knights will be well established centrally. And if black tries to sit still, <code>e4-e5</code> is a threat, leaving black's kingside heavily undefended and white's pawn push is quite straightforward, black will lack space and the ability to create a counter-attack.</p></li>
<li><p>Mid: Black prepares for the immediate <code>b5</code> (with <code>Qc7</code>) in order to reinforce <code>c4</code> which leads to: <code>Qe2, Qc7, Nbd2, e6, e4, b5, f5!</code> and soon followed by <code>a4.</code> Notice how white's perfectly undermining the entire pawn backbone (<code>e6, d5, b5</code>) of <code>c4</code>.</p></li>
<li><p>Right: Black simply tries to stop <code>e4</code> by blockading it with a knight, but since it cannot really be followed up by <code>f5</code> (as shown in the diagram), it will easily be challenged with <code>Nbd2</code> after which black either has to take on <code>d2</code> which revives <code>e4</code> again, or lets white take on <code>e4</code> leaving a ton of light square weaknesses behind along with a permanent knight post on <code>e5.</code> Note that in this structure, black has no prospect for ever landing a knight on <code>d3</code>, leaving the light square control that the overly advanced pawns have secured virtually unusable. Finally, notice that in neither of these cases, black's left with any form of initiative or targets in white's structure to allow for any counter-attack. </p></li>
</ul>

<p>Lastly, by not playing <code>c4</code>, you can still entertain a timely resolution of the central pawns in order to either simplify or create weak points in white's centre. And to connect with our discussions, by holding still with the pawn on <code>c5</code> you are actually stopping white's <code>e4</code> push as after, say, <code>e6, Nbd2, Be7, e4</code> you can simply take both on <code>e4</code> and <code>d4</code> not allowing white any central control (unlike the case of <code>c4</code> where white always had clear spatial advantage), and your structure is devoid of weaknesses. If anything, white will be the only side with potential dark square weaknesses. And if white recaptures on <code>d4</code> with the pawn, then it's a comfortable IQP structure with easy play for black.</p>

<p><a href="https://i.stack.imgur.com/wEMvvb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wEMvvb.png" alt="enter image description here"></a></p>
