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

London system 3. Bf4 White is playing the London system, where they plan to support d4 with their e3 pawn and eventually plant their knight on e5, controlled by the e pawn and the dark square bishop. Now that they have developed their bishop, they can play e3 without trapping it behind the pawn chain. The London system is a system opening, where White has the same general ideas to many Black responses and the specific orders are very flexible. This position can also arise from the Accelerated London 1. d4 d5 2. Bf4 Nf6 where 3. Nf3 transposes. Black has several approaches to the position, including ...c5 and ...Qb6 to pressure White's b2 pawn, weakened by moving the bishop away. Theory table References See also London System