tewald wrote on 05/16/15 at 14:30:03:


If you play c4 in a London system, it's no longer really the London system, being instead something you could reach from a set up with d4 and c4. You would play it if you thought it gave an advantage and it's a popular idea against Kings Indian setups by Black.

As to whether to play Be2, Bd3 (or Bc4) it may just be a style question. Be2 would be the most solid, Bd3 suggests that trying to play e3 to e4 is going to be a plan, whilst Bc4 puts the Bishop on an aggressive diagonal if Black should play .. e5. It's not available if Black has thrown .. d5 himself into the mix.

My personal preference for defending against a London is to either use a reverse Reti, in other words the structure Nf6,g6,Bg7,d6, Nbd7,c5,b6,Bb7 or a Hedgehog with Nf6, e6, Be7, d6, Nbd7, c5, b6, Bb7. Against c4 systems, you have the added option of playing an early c5, then c5xd4 and .. d5 with  Gruenfeld like positions. As to where the White Bishop goes, I have found my opponents using all three possibilities.