In the event of 4...exf5 , one of several tempting replies is 5.Ne7+! Bxe7 6.Rxe7 , followed by Rdd7.
Prophylaxis against the ...b6-b5 advance, which from now on will be met by c4-c5.
Restricting White's intended queenside advance,which could have become real after 1...Bxa3?1 2.Nxa3 , followed by Nc2, a2-a3 and b3-b4.
Preparing ...h7-h5 with an attack. Thanks to his powerful knight, Black enjoys good compensation for the pawn.
Unity Chess Club
Eingorn - Agrest Chalkidiki 2002 White to move
1.Qxa6! Nxa6 2.h6!
In order to imprison Black's bishop just before he vacates the f8-square by ...Rfe8 or ...Rfc8.