Pirc with 3. Bd3 and 4.c4 system

Hi,

(Sorry the subsject should be 4.c3 and not 4.c4)

I am trying to understand the pirc with 3.bd3 and 4.c3 system . I tried to read many pirc books but the coverage was very weak. I don't understand why white is playing these moves although it is clear to me that putting the bishop on bd3 is not very favorable for white especially when black plays 3...e5 (blocking the movement of the white's e pawn and the effectiveness of the bishop as well) and I don't understand why white plays c3. Can anyone help in that regard either by commenting on white's moves or by referring me to a book that I can read ( Pirc alert in chapter 23 doesn't show the intuition behind these moves).

Thanks

I am by no means an expert on the Pirc, but I imagine you are talking about this : 

Bd3 is protecting the e4 pawn, c3 is protecting d4 and I imagine it is there in case black plays e5 and wants to take on d4.

As you have played c3, you can not play Nc3 to protect e4 so you use Bd3.

I imagine we are not playing yet Nd2 as it would block the Bishop on c1 and we would like to move it first. (We are not going to fianchetto after c3.)

Then afterwards I see a f4 or a Nf3 all depends what we want to do

I imagine a better player will see more in this than me, but I don't see much more.

c3 also sets up a wall of pawns against your fianchetto bishop and if there's no knight on c3 White avoids some of the usual queenside pawn pushes. I think White is interested in trying to reduce Black's play before doing anything in the center. 

After 3. Bd3 Black can play 3. ... e5 which more or less gives him a comfortable position after 4. c3.

gfaq - NO, after 3.Be3?, Black should take the pawn.

I see a lot of people playing 3.Bd3 and it's a very weak move compared to 3.Nc3.  Actually, Black has an even better move than the commonly played 3...e5

After 1.e4 d6 2.d4 Nf6 3.Bd3?! Nc6! 4.c3 and only now do you play 4...e5!  Exchanging is absolutely harmless, and advancing the d-pawn leads to 5.d5 Ne7 and White has nothing better than to play an eventual c4, whether it be this move or a few moves down the road.  At that point, Black should Fianchetto his King's Bishop, and play a King's Indian Defense up a tempo (White went c2-c3 and c3-c4).