Answers.Body: <p>It is indeed a little silly to play ...Bb4 on move 2 here. That said, it often gets played a little later, and the main idea is to pin the knight on c3 (after the d-pawn has moved), so that it no longer protects the pawn on e4, which can now be attacked by a knight on f6, say.</p>
  
  <p>In the particular line you gave, by the way, the bishop is doing just fine on b6. You spent time kicking it to a place where it's aiming right at the weak pawn on f2 and beyond to your king on g1 once you castle.</p>
  
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Answers.CreationDate: 2015-06-12T00:16:47.557Z
Answers.Text: Yes, that was pretty much the only advantage I could see as well, threatening the f2 square. But even with then black's dark bishop is in a precarious position. Wouldn't it make more sense to play Bc5 and then back up one more square a bit later?
Answers.UserDisplayName: Seth
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Answers.CreationDate: 2015-06-12T00:10:33.007Z
Answers.LastActivityDate: 2015-06-12T00:10:33.007Z
Answers.UserDisplayName: dfan
Answers.Body: <p>This is an opening reminiscent of the <a href="http://en.wikipedia.org/wiki/Ruy_Lopez" rel="nofollow">Ruy Lopez</a>. Black has several goals when playing 2... Bb4:</p>
  
  <ol>
  <li><p>Move the bishop out of the way in order to prepare to castle.</p></li>
  <li><p>Set up a potential knight-to-king pin, preventing white from advancing the important central d-pawn, which white will usually want to do in order to gain better control of the center.</p></li>
  <li><p>Attack the knight that is defending the e-pawn—this isn't as immediately productive as it is when played by white, as black has no way to subsequently capture it; however, it's still a threat.</p></li>
  <li><p>If black does trade the bishop for the knight, recapturing it will ruin white's pawn structure. Recapturing with the b-pawn is a bad idea (allowing 2... Bb4 3. a3 Bxc3 4. bxc3? d5 5. exd5 Qxd5 giving black better control of the center), and hence white is forced to move the important d-pawn aside.</p></li>
  </ol>
  
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Answers.CreationDate: 2015-06-12T00:19:29.003Z
Answers.Text: 2. is pointless as it doesn't happen. 3. also seems pointless, you either exchange or are forced to back up in such a way that you aren't threatening it. It seems a bit early to be so sure 4. is a good idea. You don't even know what pawn structure white is going for! 1 seems to be the only useful gain (besides what dfan points out in his answer).
Answers.UserDisplayName: Seth
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Answers.CreationDate: 2015-06-12T00:28:46.093Z
Answers.Text: @Seth 2. does happen if white moves his d-pawn, which is usually a thing that white will want to do (in order to gain better control of the center). If black decides to trade the bishop, 3. leaves the e-pawn with nothing defending it (although white can easily fix that, which is why this (Bb4) isn't as good of a move as it is when played by white (Bb5 with a black knight on c6, i.e. the Ruy Lopez). For 4. trading the bishop forces white to recapture with the all-important d-pawn (as using the b-pawn allows 2... Bb4 3. a3 Bxc3 4. bxc3? d4 5. exd4 Qxd4 giving black better control of the center).
Answers.UserDisplayName: Doorknob
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-12T00:34:40.787Z
Answers.Text: Whoops, sorry, those last three moves in my comment should be d5, not d4 (comment too old to edit).
Answers.UserDisplayName: Doorknob
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Answers.LastEditDate: 2015-06-12T00:37:19.827Z
Answers.UserDisplayName: Doorknob
Body: <p>This happens sometimes when you're playing a person, more often when playing the computer it seems. The lichess Android app for e.g., on the easiest setting, <em>always</em> follows Nc3 this way (usually following on the first variation below).</p>
  
  <pre><code>[FEN ""]
  1. e4 e5 2. Nc3 Bb4 3. a3 ( 3... Bxc3 4. bxc3 Nf6 5. Rb1) (3... Ba5 4. b4 Bb6)  
  </code></pre>
  
  <p>Every time I see this played I wonder what black is trying to gain here. He either ends exchanging the bishop for my knight (and giving my rook a good open file) or locking his bishop in one corner, neither seems particularly useful.  </p>
  
  <p>Am I missing something? </p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-06-15T22:10:24.877Z
Comments.Text: ...Bb4 is indeed inaccurate in this position.
Comments.UserDisplayName: limits
Tags: <opening>
Title: What is black trying to accomplish when playing Bb4 after Nc3 in the opening?
ThreadText: # What is black trying to accomplish when playing Bb4 after Nc3 in the opening?
  
  (Asked by: username_0 on 2015-06-11)
  
  This happens sometimes when you're playing a person, more often when playing the computer it seems. The lichess Android app for e.g., on the easiest setting, always follows Nc3 this way (usually following on the first variation below).
  [FEN ""]
  1. e4 e5 2. Nc3 Bb4 3. a3 ( 3... Bxc3 4. bxc3 Nf6 5. Rb1) (3... Ba5 4. b4 Bb6)  
  
  Every time I see this played I wonder what black is trying to gain here. He either ends exchanging the bishop for my knight (and giving my rook a good open file) or locking his bishop in one corner, neither seems particularly useful.  
  Am I missing something?
  
  **Tags:** opening
  
  > **Comments:**
  > **username_1**: ...Bb4 is indeed inaccurate in this position.  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_2 on 2015-06-12. Score: 4
  
  It is indeed a little silly to play ...Bb4 on move 2 here. That said, it often gets played a little later, and the main idea is to pin the knight on c3 (after the d-pawn has moved), so that it no longer protects the pawn on e4, which can now be attacked by a knight on f6, say.
  
  In the particular line you gave, by the way, the bishop is doing just fine on b6. You spent time kicking it to a place where it's aiming right at the weak pawn on f2 and beyond to your king on g1 once you castle.
  
  > **Comments:**
  > **username_0**: Yes, that was pretty much the only advantage I could see as well, threatening the f2 square. But even with then black's dark bishop is in a precarious position. Wouldn't it make more sense to play Bc5 and then back up one more square a bit later?  
  
  ---
  
  ### Answer by username_3 on 2015-06-12. Score: 3
  
  This is an opening reminiscent of the [Ruy Lopez](http://en.wikipedia.org/wiki/Ruy_Lopez). Black has several goals when playing 2... Bb4:
  
  1. Move the bishop out of the way in order to prepare to castle.
  2. Set up a potential knight-to-king pin, preventing white from advancing the important central d-pawn, which white will usually want to do in order to gain better control of the center.
  3. Attack the knight that is defending the e-pawn—this isn't as immediately productive as it is when played by white, as black has no way to subsequently capture it; however, it's still a threat.
  4. If black does trade the bishop for the knight, recapturing it will ruin white's pawn structure. Recapturing with the b-pawn is a bad idea (allowing 2... Bb4 3. a3 Bxc3 4. bxc3? d5 5. exd5 Qxd5 giving black better control of the center), and hence white is forced to move the important d-pawn aside.
  
  > **Comments:**
  > **username_0**: 2. is pointless as it doesn't happen. 3. also seems pointless, you either exchange or are forced to back up in such a way that you aren't threatening it. It seems a bit early to be so sure 4. is a good idea. You don't even know what pawn structure white is going for! 1 seems to be the only useful gain (besides what username_2 points out in his answer).  
  > **username_3**: @username_0 2. does happen if white moves his d-pawn, which is usually a thing that white will want to do (in order to gain better control of the center). If black decides to trade the bishop, 3. leaves the e-pawn with nothing defending it (although white can easily fix that, which is why this (Bb4) isn't as good of a move as it is when played by white (Bb5 with a black knight on c6, i.e. the Ruy Lopez). For 4. trading the bishop forces white to recapture with the all-important d-pawn (as using the b-pawn allows 2... Bb4 3. a3 Bxc3 4. bxc3? d4 5. exd4 Qxd4 giving black better control of the center).  
  > **username_3**: Whoops, sorry, those last three moves in my comment should be d5, not d4 (comment too old to edit).  
  
  ---
  
  