Playing ...f6 in "advance" pawn structures?

As a caro-kann player as black and an e4 player as white, I feel that I need to understand this. When this (or a similar) pawn strcuture shows up...

When is it a good idea for black to play ...f6? Are there any general rules for this, or do you just have to "calculate?" I've been burned by the backwards e-pawn a few times playing it on the black side, but it sometimes is an annoying pawn break when I have the white pieces! Any advice? Thanks!

That's a known problem. I asked myself the same thing, usually in similar positions in the French. I think a grandmaster would have to answer it. This is what I know:

1) If you still have the queen's bishop on c8 or d7, the e6 pawn is actually not that weak, so you can break easier.

2) Breaking is easier when white has played Nf3 rather than f4. The move f4 also costs a tempo, so you may not have to worry at all and play elsewhere. 1...f6 2.exf6 gxf6 weakens the kingside and it leaves the e5 square in the pliers d4 and f4. While this is still playable you cannot do it when white has ueberdeckt the e-file. If you do not play gxf6 obviously e5 is a real weakness, so you have to play that very carefully and not exchange into an endgame. (2...Nxe5 fxe5 if applicable, shutting the weak square down is still ok)

3) Breaking early is easier than when white is well prepared for it. Also you need enough pieces on the board if you ever hope to accomplish an e5 break. If you can never do that, make sure you can hold the endgame. The king on f7 sometimes has to hold it I think.

4) 1...f6 2.whatever??? fxe5 3.fxe5 accomplishes virtually nothing, other than rid black of the f7 pawn. White still has a space advantage with the e5 pawn while there is complete symmetry. In the diagram d4 is already weak. Do you also want to make black pawn e6 weak, is the question.

Conclusion: It is difficult, but the key is to put some actual pressure on the white centre. You need to decide if it is d4 that is the target, or e5. Which pawn can I isolate? You simply need to build up behind your own pawns before you decide on cxd4 or f6. After all the play on the c-file (rather than attack on the centre pawns) may be enough in which case you don't need the f6 break. Hopefully white cannot cover both sides of the board and prevent all plans.

Thanks :)

Anyone else?

As White: If black tries this, there are usually a few good options.  Trade on f6 and make him solve the backwards pawn problem (which usually switches your plan), let him trade on e5 and either target the e pawn or trade off a kingside defender.  And the plan of blowing up the center with f5 and riding the complications: usually white will be able to maneuver better since the the e6 pawn constricts the light squared bishop and e5 takes away f6 from black's N/B.

As Black: the f6 break is useful when you want to keep a flexible defense.  For example, trade off the f-pawns and use the f7 square to double rooks (either to or from the c-file).  Rarely have I found f6-fxe5 useful in and of itself to consider doing; typically it's lumped with either tactical or endgame considerations (I have a R on the 2nd and can potentially double on the 2nd).

In the structure above I tend to think black would be better off trying to attack white's weak d-pawn, with moves like Qb6 and Nc6, rather than trying to break up the centre. Also doubling rooks on the open c-file could be a good plan. If the queens come off and the potential threat to black's king is eliminated, then I think black could have a good game, because white has a pawn weakness (d4) and black doesn't.

I play the classical French as black, in which white can usually maintain a pawn on either d4 or f4, but not both. In that situation, f6 can be much more effective. It can open the f-file for black's rook, and give black a 2-vs-1 central majority, and the idea of e5 comes into play. But when the e-pawn is defended twice none of this stuff is really any good.

Thanks :)