# Chess Opening Theory/1. e4/1...e5/2. d4
## Center Game

The move 2. d4 by White smashes open the center by attacking Black's king pawn and allows White to develop his pieces with very great speed by opening up the d-file for the queen and bishop.

### Black's responses

The most common response is for Black to accept the Centre Game and take the pawn with 2...exd4, which White will retake with the queen. Although no pawn material is lost here, White will lose tempo in order to save the queen from Black's Nc6 knight attack. This gives Black a lead in development, which brought this opening out of favor historically by the early 20th century although the opening has been explored later from the 1980s.
Defending the e-pawn instead with 2...d6 leads to a transposition of the Maróczy Defence stemming from the Pirc Defence (1. e4 d6 2. d4 e5). The Maróczy Defence may then lead to the Philidor. However, White can choose not to transpose here since Black's 2...d6 gives White the chance now to aggressively capture the e-pawn with 3. dxe4 rather than defend their d-pawn with the Philidor's 3. Nf3 knight defence. Once the pawns are traded off, White can force off the queens as well which denies Black the ability of castling – possibly leading into an early endgame.
Instead of the normal 2...exd4, a countergambit can be tried with 2...f5?!, but this is quite a dubious move and is only reserved for unprepared players. 2...f5 gives White a good game after the threat of Qh5+ can't be stopped (the bishop can move and give a square to the king on f8), as after 3. exf5 Nf6?? loses to 4. dxe5!, and Black has two choices: letting a very dangerous Qh5+ happen or giving up the knight. Note that trying to keep the knight on f6 to prevent Qh5+ without losing it with the move 4... Qe7 doesn't work, since white can unpin the e-pawn with 5. Qe2. After that, the black knight has to move, allowing Qh5+. Once again, unprepared opponents may be surprised by this countergambit and play recklessly, leading to possible, but rare wins by Black.

## Theory table

1. e4 e5 2. d4
| | 2 | 3 | 4 | 5 | Evaluation | Notes |
| Centre Game Accepted | ... exd4 | Qxd4 Nc6 | Qe3 Nf6 | Nc3 Bb4 | = | |
| Danish Gambit | ... exd4 | c3 d5 | exd5 Nf6 | Bb5+ Bd7 | = | |
| Nimzowitsch Defence | ... Nc6 | Nf3 exd4 | | | = | Nimzowitsch sideline by transposition after 2...Nc6 (more commonly: 1. e4 Nc6 2. d4 e5). And, can continue as a Scotch transposition if 3. Nf3 (more commonly: 1. e4 e5 2. Nf3 Nc6 3. d4). |
| Maróczy Defence | ... d6 | dxe5 dxe5 | Qxd8+ Kxd8 | Bc4 | | Also, known as the Philidor Gambit. |
| Philidor Defence | ... d6 | Nf3 exd4 | | | | By transposition (after 2...d6, iff. White plays 3. Nf3). More commonly: 1. e4 e5 2. Nf3 d6 3. d4 |
| Petrov's Defence | ... Nf6 | Nf3 Nxe4 | | | = | By transposition (after 2...Nf6, iff. White plays 3. Nf3). More commonly: 1. e4 e5 2. Nf3 Nf6 3. d4 |
| Beyer Countergambit | ... d5 | | | | | Stemming from the Blackmar-Diemer Gambit by transposition. More commonly: 1. d4 d5 2. e4 e5. |
| | ... f5 | exf5 Bd6 | dxe5 Bxe5 | Qh5+ Kf8 | +/- | Recalls a reversed Falkbeer Countergambit but White (playing as Black) has an extra tempo. |

## References

* Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.

## External links

* 365Chess: 1. e4 e5 2. d4
For explanation of theory tables, see theory table and for notation, see algebraic notation.
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