Moonbus White; Aquatabby Black; notes by moonbus; initial ratings within 30 points.
1... d6 2. d4 Ng8f6 3. Nb1c3 g6 4. f4
White is playing an aggressive variation (Austrian Attack) against the Pirc, trying to take immediate spacial advantage over Black's restrained pawn structure.
4... Bf8g7 5. Ng1f3 O-O 6. Bf1d3 Nb8a6
Black intends ... c5 and the QN to b4 or c7 at some point.
7. O-O c5
The Pirc often leads to positions in which Black strives for activity on the Q-side while White mounts an attack against Black's castled king.
8. d5
White opts for a boa-constrictor strategy, to reduce Black's mobility.
8... Bc8g4 9. Qd1e2 Na6c7 10. a4
White dominates ... b5, which is the usual liberating plan for Black in the Pirc.
10... Ra8b8
Black is following the usual plan, preparing ... b5 to get Q-side activity.
11. h3 Bg4xf3
Black is practically forced to exchange here, as retreating to d7 or c8 would only clog up his already cramped position, and the Black QB would have no prospects by manoeuvring via c8 to b7.
12. Qe2xf3 a6
Still trying for Q-side activity, preparing ... b5.
13. a5
This effectively scotches Black's Q-side plans, as ... b5 would be met by axb5 e.p. and Black's isolated a-pawn would be his Achilles' heel.
