The Pirc Defense is a really strange opening. It looks almost like the Sicilian Dragon, except White has a strong center and Black has no open 'c' file for counterplay! Yet, it is a sound opening played by many great chess players. Still, seeing such obvious similarities with the Dragon variation, I cannot help but remember the famous Fischer plan of dealing with the Dragon: just push the 'h' pawn, check, check... mate! Let's see if such a crude method works in the Pirc.
Here is a game that was played just last week:
The 6.e5!? idea is not new of course and was relatively popular in the 1960's. In the next game GM Leonid Stein showed that White doesn't really need to burn his bridges by sacrificing a piece as early as move 9, (like Nakamura did in the previous game). Still his attack was so vicious that his opponent GM Leonid Shamkovich didn't last long.
Maybe Black should just take the annoying pawn by 6...dxe5? In the following game a strong Armenian GM and a namesake of the great World Champion Tigran Petrosian shows that even in this case Black is not out of the woods.
The 6.e5!? plan doesn't refute the Pirc Defense, but does pose serious problems for Black. In the resulting positions one wrong move spells disaster for Black. Therefore, many chess players prefer to play 5...c5, delaying castling and immediately attacking White's center. In the next brilliant game White still managed to achieve a strong attack with a surprising sacrifice.
In conclusion, let me repeat my usual advice/disclaimer. It is my deep belief that a sound opening cannot be refuted. Since the Pirc Defense is definetely a sound opening, the goal of this article is not to find a refutation (which we can be sure doesn't exist). My goal was just to explain the main ideas, to demonstrate typical attacking patterns and to share the spirit of the opening. I hope you replayed the whole games and not just the positions shown on the diagrams (Remember that you can always replay a whole game from the first move if you click "Solution" and then "Move list"). If you liked what you saw so far, then it is a good starting point for your own investigation of the opening. I can tell you one thing for sure: if you decide to give this variation a try, I can guarantee you an interesting game and a lot of excitement.
Good luck!