# Chess Opening Theory/1. Nf3/1...d5/2. c4
## 2. c4 - Réti Opening

This opening is a hypermodern opening, which invites white's minor pieces to control the centre rather than their pawns. Here black has 4 options:

### Defending the Pawn

This can be done with moves such as 2... c6, or 2... e6, both of which generally transpose to the Queen's Gambit Declined or Slav Defense. However, white can deviate with 3. g3, leading the positions that resemble the Catalan Opening (or even transposing to the Catalan Opening, normally reached with 1. d4 Nf6 2. c4 e6 3. g3), or even 3. b3!?

### Advancing the Pawn

This gives black a spatial advantage in the center and a quite annoying pawn on d4 that controls c3 and e3, squares where the bishop and knight could have originally been developed to. From here, white challenges the pawn with e3, a3 (followed by b4), and b4, while black tries to hold onto the pawn with Nc6 and c5.
The most critical line in this variation is known as the Reversed Blumenfeld Gambit (similar to the Blumenfeld Countergambit played as black), going 3. e3 c5 4. b4 dxe3 5. fxe3 cxb4 6. d4, where black is up a pawn, but it's a weak pawn on b4, and white has central control and development to compensate for that. White is generally considered to get enough compensation for the pawn in this line and gets a ~52% score from it.
White can also choose to avoid this line and go for 3. g3, which leads to positions resembling the Alekhine Defense, where black has a huge spatial advantage in the center after 3... Nc6 4. Bg2 e5 5. O-O e4 6. Ne1, but the pawns are weak and white can attack them with moves like d3. This is best for people who want to follow the "hypermodern" opening ideal, where black follows the classical opening ideas, but white controls the center with pieces and targets the central pawns that black has.

### Capturing the Pawn

Capturing the pawn with 2... dxc4 isn't considered the best, but theory and practice has shown that black does just fine. This usually transposes into a Queen's Gambit Accepted line, which is usually fine for both sides. A sample line would be 3. e3 e6 4. Bxc4 c5 5. d4 Nf6, transposing to the Classical Defense of the Queen's Gambit Accepted.

### Ignoring the threat

Black can choose to ignore white's threat since black's Queen is defending the pawn and instead to develop a piece. The correct response is to capture black's pawn on d5. When black captures back with their Queen, white can develop their knight to c3 with tempo.

## Theory table

For explanation of theory tables, see theory table and for notation, see algebraic notation.
1. Nf3 d5
| | 2 | 3 | 4 | 5 |
| Queen's Gambit Accepted | c4 dxc4 | e3 e6 | Bxc4 c5 | d4 Nf6 | = |
| Fedida Gambit | ... dxc4?! | b3 cxb3 | Qxb3 e6 | e4 Nf6 | ⩱ |
| Reti Opening Mainline | ... d4 | g3 Nc6 | Bg2 e5 | O-O e4 | ∞ |
| Reversed Blumenfeld | ... d4 | e3 c5 | b4 dxe3 | fxe3 cxb4 | ∞ |
| English Opening | ... e6 | g3 Nf6 | Bg2 Be7 | O-O O-O | = |
| Slav | ... c6 | d4 Nf6 | Nc3 dxc4 | a4 Bf5 | = |
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## References

* Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.
* Flank Openings, Bruno Carlier, Trends publications, 1990. No ISBN
* Winning With The Reti Opening, Ken Smith John Hall, Chess Digest Inc., 1993, ISBN 0-87568-237-5
* This Chess related article is a stub. Please assist Wikibooks by expanding it.