Classical Variation

The Classical Variation, also called the Two Knights System, arises when White answers the Pirc setup with 4. Nf3. White develops the king's knight to its natural square and is content with the pawn pair on d4 and e4, declining the more committal f2-f4 of the Austrian Attack. The knight reinforces d4 against Black's later ...c5 or ...e5 breaks, and White's plan is simple development, kingside castling and use of the space advantage, rather than an early attack. It is classified under ECO B08.

Black almost always replies 4...Bg7, continuing the fianchetto and preparing to castle. The Quiet System, 5. Be2, is the most common treatment. After 5...O-O 6. O-O both kings are safe, and Black builds a compact position and waits for the right moment to strike at the center. One such moment is 6...c5 7. Be3 cxd4 8. Nxd4, which transposes to a Sicilian Dragon structure. The same Quiet System position can also be reached through 4. Be2 Bg7 5. Nf3.

The Schlechter Variation, 5. h3, spends a tempo to take g4 away from Black's light-squared bishop, so that the f3-knight cannot be pinned, and keeps open a later Be3 without the risk of ...Ng4. A less frequent choice is 4. Nf3 Bg7 5. Bg5, a version of the Byrne idea with the knight already developed. At move four, Black occasionally deviates from the fianchetto: 4...Bg4 pins the knight at once and puts pressure on d4, while 4...c6 delays ...Bg7 in favor of queenside flexibility. Engines also consider 4...a6 a reasonable alternative, with the idea of ...b5, though it is seldom played.

The variation has a reputation as a sound, low-risk way to meet the Pirc, and the play tends to be slower and more positional than in the Austrian Attack or the Be3 and Qd2 systems. Efim Geller, Anatoly Karpov and Evgeni Vasiukov all used it successfully with White, while Zurab Azmaiparashvili achieved good results defending the Black side. It ranks among the more frequently reached named positions in online play, where results are close to even; engines assess the position as a slight edge for White.