Chess Opening Theory/1. d4/1...Nf6/2. Bf4/2...d5

Accelerated London system Accelerated London (Closed game) Accelerated London (Indian defence) 3. e3 3. Nc3 · Rapport-Jobava London (transposition) 2...d5 Black's most common approach to combating the Accelerated London is with both Nf6 and d5, whether they began with the Indian defence 1...Nf6 or the Closed game 1...d5. White's plans in the London system are generally to to play e3, c3, Nd2, Bd3 in some order, and plant their kingside knight on e5 via Nf3. 3. e3 is the most common move order. This defends d4 and prepares to develop Bd3. Once Nf3 is played, e.g. 3. Nf3, the opening has converged with the regular, non-accelerated London. 3. Nc3, instead of playing c3, transposes to the Rapport-Jobava London. Black's two main approaches involve 3...c5 or 3...e6. The idea behind the 3...e6 line is to play 4...Bd6, getting ready to castle quickly and threatening to trade off White's London bishop. White can drop their bishop back to g2, inviting Black to trade but after hxg2 White gets the semi-open h-file in return. In the e6 lines, Black's light square bishop often has difficulty developing. This approach resembles a Semi-Slav defence with colours reversed. The ...c5 line has the idea to to prioritise ...Bf5 and ...Qb6 before finishing developing the kingside and castling. Black seeks counterplay by pressuring b2, which White left undefended when they moved their bishop early on. (White does not want to take the offered c5 pawn of course: they'd rather play c3 and let Black trade into them, so that they can keep two pawns in the centre). Having committed to d5 already, the King's Indian-style approach with 3...g6 is less common but still playable. Black continues 4...Bg7, and 5...O-O. White usually includes h3, so there is a retreat square for their bishop on h2, and Be2. 1. d4 d5 2. Bf4 Nf6 3. e3 e6 4. Nd2 Bd6 5. Bg3 O-O 6. Bd3 c5 7. c3 Qc7 The ...e6, Reverse Semi-Slav approach: mainline position after 2...Nf6 3. e3 e6 4. Nd2 Bd6 5. Bg3 O-O 6. Bd3 c5 7. c3 Qc7. 1. d4 d5 2. Bf4 c5 3. e3 Nc6 4. c3 Nf6 5. Nd2 Bf5 6. Ngf3 Qb6 The ...c5 approach. Steinitz countergambit mainline, after 2...c5 3. e3 Nc6 4. c3 Nf6 5. Nd2 Bf5 6. Ngf3 Qb6. 1. d4 d5 2. Bf4 Nf6 3. e3 g6 4. Nf3 Bg7 5. h3 O-O 6. Be2 c5 7. c3 Nc6 The ...g6, King's Indian-style approach, after 2...Nf6 3. e3 g6 4. Nf3 Bg7 5. h3 O-O 6. Be2 c5 7. c3 Nc6. Theory table . 1. d4 Nf6 2. Bf4 d5 3 (to) Main Line ...e3 = References London System Bibliography Win with the London System. 2005. Sverre Johnsen, Vlatko Kovačević. 1-9046-0035-2. Chess Opening Crash Course: The London System __NOTOC__