White'sQKt2(b2) Pawn exchanges
Kt-for-B on QB3(c3), taking Black's dark
checking bishop. Black advances his KBPawn to KB4(f5)
planning ..Kt-KB3 after, and deters P-K4.
White Black
1. P-Q4 P-KKt3
2. P-QB4 B-Kt2
3. Kt-QB3 P-QB4
4. P-Q5 BxKt ch
5. PxB P-B4