White's K2(e2) knight removed Black's doubled KBP on
KB4(f4) and took control of Q5(d5). Black develops his Queen to K2(e7),
pinning the White KP to prevent 5..P-Q4, 6.PxP or
5.P-K5, 6.PxKt.
White Black
1. P-K4 P-K4
2. Kt-K2 Kt-KB3
3. P-KB4 PxP
4. KtxP Q-K2