Chess Opening Theory/1. d4/1...Nf6/2. c4/2...e5/3. dxe5/3...Ng4

Budapest defence A51-A52 Budapest defence 3...Ng4 Black saves their knight and attacks the e5 pawn. White can choose to give the pawn back now or later in return for space and/or piece development. It is possible for White to hold onto the pawn, but at a positional cost. The main options are 4. e4, 4. Nf3, or 4. Bf4. Give back the pawn 4. e4, the Alekhine variation gives the pawn back immediately in return for taking space in the centre. 4. e4 increases White's control over d5 and reveals an attack on Black's knight, so Black's move is almost always 4...Nxe5 5. f4 and Black chooses between 5...Nec6 or 5...Ng6. One idea for Black is ...Bb4+, hoping for Nc3 Bxc3+ bxc3 leaving White with doubled isolated c-pawns. 4. Nf3, the Adler variation, develops a piece while defending the pawn. Black can force White to give back the pawn in this line because of the move 4...Bc5: this compels White to play 5. e3 to end the pressure on f2, so White cannot then play Bf4 and so cannot bring enough defenders to the pawn. (Anything other than 5. e3 is a horror show, e.g. 5. Bf4?? Bxf2+ 6. Kd2 d6 7. exd6 Qf6 8. e3 Nxe3 9. Bxe3 Qxb2+---). After 5. e3, White can concentrate on development and let Black pick up the pawn. A continuation is 5...Nc6 6. Nc3 O-O 7. Be2 Re8 8. O-O Ngxe5 9. Nxe5 Nxe5. A common middlegame plan for Black is to rook lift with ...a5, ...Ra6, and ...Rh6. Alternatively 4...Nc6 allows White to bring in the bishop to defend the pawn, 5. Bf4, and transposes into a Rubinstein variation. Keep options open for now 1. d4 Nf6 2. c4 e5 3. dxe5 Ng4 4. Bf4 Nc6 5. Nf3 Bb4+ Main line, position after 4. Bf4 Nc5 5. Nf3 Bb4+. 1 right 4. Bf4 is the Rubinstein variation and main line continuation. Here 4...Bc5? is a mistake because 5. e3 obstructs f2 and discovers an attack on Black's knight: 5...d6 (to allow the queen's bishop to defend the knight) 6. exd6 cxd6 and White gets to stay a pawn up. The continuation then is 4...Nc6 5. Nf3 Bb4+ and White then has to decide how badly they want to keep the pawn (see diagram). Black has two attackers on e5 and can bring a third with ...Qe7. White has two defenders, and to bring a third will need to play Qd5: Blocking the check with 6. Nc3 keeps the option of Qd5 open but allows 6...Bxc3+ 7.bxc3 and White's doubled, isolated c-pawns will be a long-term weakness. The main line is 6. Nd2, blocking the check and preventing Qd5 so allowing Black to win back the pawn after 6...Qe7. But either approach is playable for White. A famous trap is 6. Nd2 Qe7 7. a3 (attacking the bishop?) Ngxe5 8. axb4?? Nd3# (the e-pawn is pinned by Black's queen). Cling onto the pawn at all costs? 4. Qd5?!, to defend the pawn and attack Black's knight, is a mistake. 4...d6 attacks the pawn and lets the queen's bishop defend the knight, and ...Nc6 to kick the queen is on the way. 5. exd6 (to "cash in" the pawn) lets Black's bishop develop 5...Bxd6 and White must be careful not to blunder ...Bb4+ discovered attack on White's queen. With 4. f4? White is determined to hold onto the pawn, but it comes at a high cost. After 4...Bc5 White must avert the threat of Bf2+ or Nf2 with a fork and easily falls behind, e.g. 5. Nh3 (defends f2) O-O 6. e4 (readies bishop to develop, and discovered attack on Black's knight) d6 (defends knight) 7. exd6 Re8-- threatens ...Rxe4+ Be2 Qh4+. Theory table 1.d4 Nf6 2.c4 e5 3.dxe5 Ng4 4 5 6 7 8 Adler variation Nf3Bc5 e3Nc6 Be2O-O O-ORe8 Nc3Ngxe5 += Rubinstein variation Bf4Nc6 Nf3Bb4+ Nbd2Qe7 e3Ngxe5 Nxe5Nxe5 += ...... ...... Nc3Bxc3+ bxc3Qe7 Qd5f6 += ...g5 Bg3Bg7 Nf3Nc6 Nc3Ngxe5 Nxe5Nxe5 += Alekhine variation e4Nxe5 f4Nec6 a3a5 Be3Na6 = e3Nxe5 Nh3d6+ Nf4g6 Nc3Bg7 Be2O-O += References See also Budapest Gambit