Chess Board
[ECO code C41]
PHILIDOR'S DEFENCE
"Queen's Knight" Variation
White's king's bishop to QB4(c4) targeted KB7(f7) for a 5.Kt-KKt5.., 6.KtxBP fork, and enabled 0-0.
Black develops Queen's Bishop to KKt5(g4) and pins White's KKt to prevent P-Q4(d4), set for 5.0-0..Kt-B3, 6.P-Q3..B-K2, 7.B-KKt5..0-0 with equality.
	White   Black
 1.	P-K4    P-K4
 2.	Kt-KB3  P-Q3
 3.	Kt-B3   Kt-KB3
 4.	B-B4	B-Kt5
Example ends: Undo or Jump or Clear