Capture the c-pawn, so the opponent has an IQP but improved development, or let them push the c-pawn and form a queenside majority?

Question

This dilemma occurs in a variety of positions.

[FEN "r1bq1rk1/pp1nbpp1/5n1p/2pp4/3P3B/2NBPN2/PP3PPP/R2QK2R w KQ - 0 10"]

Here, it's white to move, and white has to choose between:

1. capturing black's c5 pawn, giving black an isolated queen's pawn, but we improve black's development with tempo,

2. make a developing move, thereby allowing black to play c4 on the next move, which creates a queenside majority of pawns, and can be dangerous later in the game.

This position is from Vasile vs. Voiculescu, where white chose to play a developing move (Rc1), and subsequently resigned after black eventually promoted the c-pawn.

Examples of famous players facing similar dilemmas: Short; Dreev; Giri. They have different positions and make different decisions.

Question: How do we decide whether we should do 1. or 2.?

Here, I don't simply mean in this specific position. I'm seeking general guidelines (or rules) as to when it is better to take, and when it is better to not take.

Answer 1

A few general guidelines:

• Take if your opponent has to waste a move to recapture. Normally this happens once your opponent has moved the f8/f1 bishop. In the position you posted, Black can take back with the knight and continue developing.
• Don't take if you've got a powerful position and are planning some aggressive attack. An attack often requires a good structural foundation in the centre, so taking on c5/c4 would compromise that.
• Take if there are a few pieces exchanged off, since your opponent's extra activity from the IQP will be less dangerous without many pieces. Take especially if the queens are off, or if your opponent is missing their dark-squared bishop (assuming your opponent is playing Black).
• Take if your opponent is behind in their queenside development. Undeveloped pieces ==> less activity ==> less danger from an IQP.
• Don't take if your king's position is compromised. The last thing you want with a vulnerable king is to have your opponent get more activity for attacking.

These rules don't always work, but it's useful to take them all into account before making a decision.

Answer 2

If you don't take on c5, your opponent can get in the move b7-b6. If b7-b6 is played, then you'll most likely be playing against hanging pawns if you take on c5. Those positions may or may not be suited for your style, which would affect your decision.

The pawns pushing to c4 would not be a threat, as you can easily get in b3 and e4 to chip away at his center.

Taking on c5 immediately would result in a classic IQP position where your goal would be to exchange minor pieces in order to stifle his attack and to keep the "heavy" pieces on the board in order to make it easier to take attack his pawn.

Answer 3

Here taking the pawn does a number of bad things -

1. It gives up the centre
2. It resolves the tension
3. It gives the opponent a good freeing, developing move, Nxc5. This develops the knight and opens up a diagonal for the c8 bishop.

In short, it is just bad. You should just continue with development. That Vasile chose Rc1 suggests that he wants to reply to c4 with Bb1. I think an immediate c4 by black is also bad because it resolves the tension unnecessarily so I would probably just castle here as white.