Chess Opening Theory/1. d4/1...Nf6/2. Bf4/2...d5/3. e3/3...e6/4. Nf3

= London System Main Line with ...d5 =

The London System is a solid and flexible opening system for white that can be played against various setups by black. After the moves:


 * 1) 1. d4 d5 2. Bf4 Nf6 3. e3 or
 * 2) 1. d4 Nf6 2. Bf4 d5 3. e3

The main ideas for both sides in the London System's main line are:

For White:


 * 1) Development and Structure: Nf3, Be2, c3, and often Nbd2 followed by a potential e4 break or the more restrained h3 and O-O. The pawn on d4 and the pawn on e3 provide a solid central structure.
 * 2) Queenside Expansion: With moves like a4-a5 or a queenside pawn storm with b4, aiming for a potential minority attack.
 * 3) King Safety: Usually achieved with O-O. The rook on f1 might later swing over to the c-file or e-file.
 * 4) Central Break: Depending on Black's setup, White can aim for e4 at some point.

For Black:


 * 1) Challenge the Bishop: ...c5 or ...Nh5 can be played to challenge White's strong Bf4.
 * 2) Development: e6 followed by Be7, O-O, and Nbd7 or Nc6. Depending on the situation, the light-squared bishop can be developed to d7, f5, or g4.
 * 3) Central Control: Black usually maintains a pawn on d5 and can consider playing ...e5 under the right conditions.
 * 4) Queenside Counterplay: Black can look for counterplay with moves like ...a6 and ...b5, depending on White's play.

Theory table
. '''1. d4 d5 2. Bf4 Nf6 3. e3'''