London & Bf4 Against the Pirc
When you put together a London system repertoire you have to choose what to do against the KID/Grünfeld, g6-setups.
One way is to play it in typical London fashion with Bf4, Nf3, e3/c3, h3, and focus on the queenside. This is recommended in most London books that I've seen. Yet, I've never tried doing this myself since there is a completely different, much more cunning option: the Jobava Attack with Bf4 and Nc3, threatening e4. The idea is to force Black to choose between a Grünfeld setup which occurs when he stops e4 with 3...d5 and a transposition to the Pirc which occurs when he plays the natural 3...Bg7 and we play 4. e4!. Either way, Black is deprived of his KID.
The first thing to realize is that we could get our starting position from the normal Pirc move order: 1. e4, d6. 2. d4, Nf6 3. Nc3, g6. 4. Bf4. Yet, in this move order, the main dark-squared bishop move is 4. Be3 and the second main option is 4. Bg5. Let's compare all three:
- The d4 point. Be3 defends the central d4 point, whereas Bg5 and Bf4 don't.
- The e5 point. Bg5 and Bf4 both put pressure on the e5 point, the Bf4 especially allows for e4-e5 in some lines.
- Bishop safety (it should be obvious that White doesn't want to lose the bishop to a knight). Be3 is relatively safe, but somewhat susceptible to Ng4 (you can't really play f4). Bg5 is susceptible to h6, g5 & Nh5. Bf4 is somewhat susceptible to Nh5 (but then you can just draw it back to e3) and could get hit with e7-e5 with tempo.
- Kingside expansion. Be3 doesn't get in the way of anything, but doesn't really allow f4 for tactical reasons. Bg5 encourages f4, but blocks a potential g4-g5. Bf4 blocks f4, but nothing else.