Bishop takes knight, why?

Hi guys!

Something I've been wondering is why is bishop takes knight played for white? Besides the Ruy Lopex exchange variation Lol

I was assuming it was done so that when Black castles they don't have the knight for protection of the castled king. However I always hear and agree that having two bishops vs one is a big advantage. Confused Lol

Advantage of two bishops doesn't exist until a certain level of technique and endgame ability is reached... I really believe that.  IMO when GMs gush over "oooh, the bishop pair" just ignore them because as you pointed out there are openings where you give it up very early and there's no way you can see for yourself why this is so.

That said, there are pros and cons to every move.  A very common idea is you give up a bishop to damage the pawn structure.   You see this in Frenchs, Caros, Nimzos, Ruys, Sicilians... probably every opening lol.

Another is because you're planning on putting most your pawns on the same color in a closed position with static structure, so that bishop was going to be your worst minor piece, and so you trade it off early even if it doesn't damage the pawn structure.

Other times it's to weaken something in the enemy camp.  Like you said, the king's knight is an important defender, so that's one reason in some lines.  Other times it's to weaken the central squares the knight defends.  Maybe you're attacking a central pawn or trying to push one of your pawns into the center, post a piece there, or just gain more central control in general.

The reasons are usually structural - many GMs think it prudent to trade a bishop for a knight just to double the opponent's pawns and saddle them with a structural weakness (as is done in many positions of the Nimzo Indian). Sometimes the reason is strategic - getting rid of a particularly dangerous knight (which might even be worth a rook - depending on the position). 

However, at the lower levels where you and I play, the answer is often "no reason at all." Low-rated players take pieces just to take them and give checks just to give them - whether or not it's a good idea. 

Yeah that makes sense. I actually watched a video yesterday where Akobian talked about trading his light square bishop in the Caro Kann because it was his worst piece. But about the pawns. Are you saying that the color of the bishop you just traded is where you are going to place your pawns? 

Thanks for the insight!!!

Re: putting pawns on the color of the bishop you traded.  Yeah, here are some examples from a caro two knights, nimzo Hubner, english defense, and french fort knox.

This is actually a good moment to show a fundamental difference between two openings:

The Caro-Kan:

And the French:

The fundamental differences between these two positions are (1) the placement of the bishop (traded profitably in the Caro - emaciated on c8 in the French) and (2) The orientation of the c pawn (which breaks the center immediately in the French and requires an extra turn in the Caro). Simplistically speaking, there's the concept of a 'good' bishop (which is NOT on the same color as most of your pawns) and a 'bad' bishop (which IS on the color of most of your pawns). The light squared bishop is 'bad' in both of the examples above - the question is whether you trade that bad bishop or try to improve it as the position opens later in the game. 

Maurice Ashley routinely says something along the lines of "bishop takes knight is a GM move".

In some positions, a knight is strong enough that it's worth trading your bishop for it.  It could have a dominant spot on the board or could be a key defender against your kingside attack.

When you ask them why they traded their bishop for the knight, they'll respond with "I dunno, I just hate knights" or another similar explanation.

What would be the reasons for doing this?

I can see how it makes things somewhat uncomfortable for White's LSB since so many squares are off-limits.

Are the other reasons? (Is my reason even correct?)

^^ I think a lot of it is just taking out frustration on the knight. Many players *expect* to win something immediately (hence the commonality of the Fried Liver in low rated games), so when you ignore them or just respond calmly by defending their threats, they want to show that they have influence on the position "I take your knight! I check your king! I will not be ignored!!"

Well said.

I've often felt this way with the moves some of my opponents make. Especially in blitz games.

I guess you're asking about the 1st diagram?

I think 5...e6 is played after... looking at black's half of the board so to speak, and not playing against white's bishop.

First of all d5 is threatened, so it's either e6 or Nf6.  But even after Nf6 black usually plays e6 later.  Not only does e6 support his central pawn, his structure and DSB compliment each other very well.  Together they protect all the squares (both black and white) while not getting in each other's way.

This isn't to say that after white plays d4 (as he often will) that black wont play e5 or c5 later.  But right now it's premature (need to develop pieces before opening lines).  And there's no reason to seek this as black is completely comfortable.  No weaknesses plus all the ideal goals are met:  a pawn he can maintain in the center, central squares for the pieces, and being able to castle.

If later on in the middlegame black decides to keep things more closed (i.e. doesn't seek e5 or c5) then it could be playing against white's bishop in the sense that white has the bishop pair, which work best on an open board.

May be true.  My diagrams are actual opening lines though.  First two are GM level for sure.  2nd diagram is an opening Fischer played as black and beat Spassky in their 1972 match. 

Last 2 not so much GM stuff, but are very playable.

Oh, I know that your diagrams are book positions, but I think the OP was asking "Why do 1100s take knights with bishops?" not "Why might Gata Kamsky trade a bishop for a knight?"

Haha ok :)

Isn't that puchline to the question "Which do you enjoy more, chess or sex?".

Did you recently buy a book of puns and other grammer tricks?

Oh crap.

Actual LOL

Sure.

People in our blitz rating range let their pawn structures go to crap all the time.

Also, the forking power of the knight becomes much more useful when your opponent is under time pressure.