Main Line (...e6 and ...Bd6)

The idea

After 3...e6 4.e3 Bd6 5.Bg3 O-O 6.Nbd2 c5 7.c3 Nc6 8.Bd3, White's setup is complete. The bishop retreats to g3 rather than allow ...Bxf4, and Black challenges the center with ...c5.

Plans for White

Castle, then play for Ne5 and a kingside attack with Qf3 or Qe2 and f4, or prepare e4 to open the center. If Black trades on g3 with ...Bxg3, recapturing with hxg3 opens the h-file for White's rook.

Plans for Black

Keep up the pressure on d4 with ...Qc7 or ...b6 and ...Bb7, and look for ...e5 to free the position. Trading White's dark-squared bishop with ...Bxg3 takes away one of White's best pieces.

Watch out for

For Black, the bishop on d3 and the knight on e5 aim at h7. With White's queen able to reach h5 or f3, castling and then leaving the kingside short of defenders can allow a quick attack.

For White, the d4 pawn. With Black's pawn on c5 and knight on c6, d4 can be exchanged, and White must make sure the resulting structure isn't weak.