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

= London System Main Base Position with ...d5 =

The London System is a Queen's pawn opening where White develops their dark-squared bishop to f4 in order to provide additional flexibility in what will become a closed position. After Black develops to d5 and Nf6, White plans to place their King's knight on f3 and pawns on e3 and c3 to strengthen their center before developing the light-squared bishop to d3. It can be used against nearly all of Black's common responses to 1. d4, including 1...d5. From this position, White usually plays 3. e3 or 3. Nf3 for the London System, or less commonly 3. Nc3 for the Jobava London System.

The Main Position of the London System, 1. d4 Nf6 2. Bf4 d5, can be reached via the Queen's Pawn Opening after 1. d4 d5 2. Bf4 Nf6.

Sometimes, the initial position setup is sometimes called the "Accelerated London System" or "Mason Attack" because James Mason was historically the first chess player to introduce 2. Bf4.

For a general introduction to the London System, take a closer look at 1. d4 d5 2. Bf4

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