This was my favorite move when I faced the Ragozin. The idea is to bring the black knight to c6, where it is well known that it is not well placed, in front of the c-pawn, in positions with this structure.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... d7d5  4. b1c3  4... f8b4 The Ragozin Defense always makes its appearance in elite tournaments.