Chess Opening Theory/1. e4/1...d5/2. exd5/2...Qxd5/3. c4

With 3. c4?! White thinks to gain space in the centre while gaining tempo on Black's queen. White gets to play another pawn move in the opening but without losing tempo, and this way, they think, they can develop Nc3 without blocking in the c-pawn and let both knight and pawn get to where they'd like to go.

However there are drawbacks to this approach. For one thing, playing c4 with tempo means Nc3 isn't played with tempo, and Nc3 would have also developed a piece.

For another, playing in this order makes it harder for White to achieve d4, which takes control of the centre while moving the pawn out of the way of both bishops:

If 3...Qa5!?, the usual Scandinavian move, White's d-pawn is pinned and Black has time to increase their control of the centre before White can get in d4. After 4. Nc3 e5 5. Nf3 Nf6=, White can play d4 but can't keep it there. If 4...Nc6 instead, this allows d4 but after 5. d4 Bf5 Black has the threat of ...Nb4 and ...Nc2+, and they are ready to castle long, exerting pressure on the d-file, while White's pieces are mostly still at home.

The most critical move however is 3...Qe4+. After White blocks the check with 4. Ne2 or 4. Be2, Black wins a pawn with 4...Qxc4 or 4...Qxg2 respectively.

Though 4. Qe2 Qxe2+ avoids dropping the c4 or g2 pawn, the resulting position favours Black. Black can develop smoothly with ...Nc6, ...Bf5 and ...O-O-O, and make better use of the half-open d-file than White can of the e-file. For White, without the queen's support it can be harder for White to actually achieve d4 and this makes it more difficult to develop actively. In some lines, Black has tactics involving ...Nxc2+ that White's queen used to defend.

If the bishop recaptures, 5. Bxe2 Nc6 6. Nf3 e5 and Black's control over d4 makes it hard for White to play d4 and free their bishops. d3 instead may help the queenside bishop into the game, but White can end up stuck nursing the backwards pawn 7. O-O Bf5 8. d3 O-O-O 9. Rd1∓.

If the knight recaptures, 5. Nxe2 Nc6, then although White's knight supports d4, they still cannot play it yet on account of the tactic 6. d4 Nb4! threatening both ...Nc2+ with a fork or (say 7. Na3) ...Nd3+ winning the pawn on f2. White's queen used to defend c2 but no longer. Playing around this threat with, say, 6. a3 first to control b4, gives Black time to play ...e5 and clamp down on d4.

When contributing to this Wikibook, please follow the Conventions for organization.

For explanation of theory tables, see theory table and for notation, see algebraic notation.