Have been studying the Pirc this week, using Chess Position Trainer and Chess Developments: The Pirc by James Vigus. It is his updated work from TPIBAW (The Pirc in Black and White). I had been playing both the Kings Indian Defense, and the Benko this week, however if white holds back c4, or starts with 1.Nf3 its hard to judge his intensions at first. Without c4 after d4 there is no KID, and I haven't yet looked more into 1.d4 Nf6 2. Nf3 c5 lines trying to reach a Benko.
Delaying with 1.d4 Nf6 2. Nf3 d6 to reach a KID seemed like a plan, and after Nc3 and e4, one might reach a Pirc. I also sought to find another opening to play vs 1.e4, so the Pirc did seem logical to learn, though it is quite different from the KID with it's pawn storms, and quite tactically rich! One mistep in move order for either side, and its disaster.
This all seemed quite fine, I studied the Austrian attack for a few hours, and trained the lines. I was a little excited to try some ideas out, and started a 30min game.
What struck me with white's play, is that it follows along with a book I have previously mentioned, A Cunning White Repertiore (ACWR), in which it recommends d4 followed by Nf3, holding back c4 until there is a pawn target on d5 to lever against. But also, this seems to divert around the KID (no c4), and the Grunfeld (But perhaps playing the fianchetto variation if it occurs) on your terms.
So, what was learned? If I want to transpose from d4 to Pirc, I must play d6 first, to at least allow e4, and then if c4, we can go back to KID lines. Should look more into the ACWR book more, it seems more sensible than I first have thought (and I need a white repertiore badly!), and, if things work well, look back into Kaufman's Black & White for reference (also a d4 repoertiore book for white).
Also, have learned the Pirc is very tricky to play, there were several lines in the book I had to turn the engine on because I could not follow the tactics. Its nice to have Chess Position Trainer in these cases. If I don't see something I play the move for the opponent, and enter the engine move, and can also mark the position as a "memory marker" if need be. If you have not seen this tool, I recommend you google it!