Trade off's

Hi all,

 Cann annyone tell me if in general a trade (say a bishop  for a knight) that forces the opponent to split his pawns in order to retake is generally a good idea. (i.e. pre trade white has pawns on a7 and b7 but after he ends up with pawns on a7 and c6.

does this generally weaken white. And in general is it a trade worth making to weaken an opponents position like this without really gaining material? 

Generally no, but there are some certain openings that rely on this.

moving a pawn from b7 to c6 in the beginning will often create doubled pawns, a pawn weakness, and an isolated pawn on the A file.  But this is offset immediately by the fact that of course you no longer have a bishop pair.  But what you may not realize is now the B file is open for your opponents rook!  This helps out your opponent, oh no!  

As a rule, don't do it, unless you are sure you can get an immediate secondary benefit, or for deeply analyzed reasons (and i mean DEEPLY.  Like, for weeks/months by a grandmaster and rybka deeply)

It depends! Thats always the answer in chess. There no rigid rules on best moves except checkmate.

Anyway, the picture painted so far is a little misleading. You dont need to analyse ''Deeply'' to know if exchanging a bishop for knight or vice versa is good or bad. In a situation were you have a bad bishop, you can sometimes see in an instant that exchanging this burden for your opponents superior knight (or bishop!) is neccessary. This is not even an option in some cases (ie. debating trying NOT to get rid of an inferior piece), and you should struggle your best to exchange. So he question you must ask is which minor pieces are superior or inferior. This is covered in Jeremy Silmans ''how to reasess your chess'' and is a wonderful read.

Okay, so you decide to exchange your bishop for knight but you lose the ''two bishops''. This is not always bad because you may have advanced outposts for your powerful knights, while in a closed position your bishops may prove a little useless (at least in the middlegame).

Taking the Sicilain Sveshnikov for example. (and other sicilians where black has played d6, e5 set up). Black wants to push d6-d5 to rid his backward pawn which lies on a half open file. A bishop on b7, a knight on f6, a knight on e7 and support from rooks or queen on the d file will support the d5 push. Of course, black cant neglect all other aspects of the board in this time. To prevent black playing the freeing ...d5 push white straight away plays his bishop to g5 to take the knight on f6. This considerable slows blacks progress regarding d5 so exchanging can also be because of control over key squares. 

As pointed out already, when you exchange like the example you gave and you have pawn on a7 and c6, the b file is now open. This file is only important to your opponent if a rook was there it would be more active and it ties in with the plan of his other pieces. Pieces must work in harmony. So, the open file must be part of favourable imbalances since thats the area you should 'play' so to speak. If the open (semi or otherwise) file provides infiltration to the 6th or 7th (or indeed 8th) ranks then allowing your opponent this may be unwise. In saying that, you may need to give a little to get a little (for example: you may have just exchanged a potential defender from your opponents king and your about to launch a mating attack; in the process you have given your opponent counterplay on the queenside with a rook on the 7th. Which is more important that is what you need to decide).

Weakness in pawn structures are static (dis)advantages but exchanging to weaken your opponents structure may have long term benefits it may come at the price of giving up the initiative (dynamic) or it may give your opponent lead in development if you are losing tempi ( dynamic).

I strongly recommend reading Silmans book(s). I see exchanges in games here and it is clear sometimes that people just lack understanding of the middlegame. It is hard to re-iterate all the ideas in the book so i suggest you get a copy of the book. Another book which i came across that might bebfit you is called ''Chess strategy for the tournament player'' (Comprehensive chess course) by Alburt and Palatnik. Best of luck with the study!

 Without going into too much detail: you may have weakend your opponents pawns (long term) but at the same time you have opened files against your king(short term). White is now able to attack your king using the half open file with the aid of the bishop on d3. This may cause you to damage your pawn structure while at the same time you have to fend off an aggressive attack. Whites bishop is superior to blacks knight, so white is now winning. (note: white has Bxh7+ unleashing rook attack on queen if the Knight were to move) Its difficult to suggest a good move since in bad positions sometimes all moves just look bad! Perhaps bringing the bishop to g6 was a better idea than exchanging for the enemy knight. On g6 the black bishop would challange whites attacking bishop. If exchanged, yes, you have weakened your kingside but your opponent would not have a half open file to hammer away at you. insted, he might have to go about 'creating' one rather than you giving him one in the first place.

Hope that helps a little. I didnt analyse the position in great detail, just general observation. 

 Pawns are also discussed in the book. All sorts of pawns too!Its amazing =)