London System

The Indian Defense: London System arises when White answers the Knights Variation, 2. Nf3 e6, with 3. Bf4. This develops the queen's bishop outside the pawn chain before e3 closes it in. Against the Accelerated London, 2. Bf4, this move order has several advantages. It keeps other setups available for longer, rules out an early ...e5, and gives d4 extra protection. That protection matters against ...c5 and ...Qb6, since the bishop's departure leaves b2 undefended. The cost is that the characteristic London formation is delayed, which gives Black time to choose a setup. The system takes its name from the London tournament of 1922.

Nearly half of all games continue 3...d5, which transposes to the London System with ...e6. White then completes development with e3 in the usual way. The main independent try is 3...c5, which strikes at d4 before Black commits the d-pawn and keeps ...Qb6 in reserve; it produces the best results for Black. 3...b6 prepares a queenside fianchetto in the manner of a Queen's Indian. Engines rate the position as balanced, and White scores slightly better in online play.