2.Bg5. This is a hard move to understand. It makes 2...Nf6 doubtful, since 3Bxf6 doubles pawns and makes Black's game more difficult. Black usually plays 2...g6 to fianchetto his bishop before he plays ...Nf6. 2...g6 marks the Leningrad variation of the Dutch defence. The bishop cannot be chased successfully: 2...h6 3.Bh4 g5 4.Bg3 f4? 5.e3! threatens mate, and so wins the pawn on f4.