Chess Board
[ECO code C21]
TRANSPOSITION
CENTRE GAME to PETROFF DEF. (Steinitz A.)
White developed his KKt for a Q-supported attack against Black's newly doubled QP on Q5(d4).
Black transposes into the Steinitz Attack line of Petroff's Defence by developing his King's Knight to threaten White's KPawn. White often transposes further by 4.B-QB4 for the Urusov Gambit. B-Alt.
    White  Black    Transp.White Black
 1. P-K4   P-K4		  (1.)
 2. P-Q4   PxP	    (2.	Kt-KB3 Kt-KB3)
 3. Kt-KB3 Kt-KB3   (3.	P-Q4   PxP   )
Continue: Transpose or Undo or Jump or Clear