White develops his Queen's Knight to
QB3(c3) to defend his KP under attack, and
prevents ..P-Q4. Black advances his King's Pawn to attack
White's knight in the centre, and plans 6..B-QKt5.
White Black
1. P-K4 P-QB4
2. Kt-KB3 P-QR3
3. P-Q4 PxP
4. KtxP Kt-KB3
5. Kt-QB3 P-K4