Chess Board
[ECO code A40]
POLISH DEFENCE
Black's pawn advance to KB4(f5) doubled an attack on White's KP, to tempt it forward or off-centre.
White pushes his own King's Bishop's Pawn out to KB3(f3) to double the defence of his threatened king's pawn, for a game generally favourable to White.
	White	Black
 1.	P-Q4	P-QKt4
 2.	P-K4!	B-Kt2
 3.	B-Q3	P-KB4!?
 4.	P-KB3
Example ends: Undo or Jump or Clear