Transpositions

- 1.d4 d5 2.e4 or 1.e4 d5 2.d4.

- 1.e3 e6 2.Nf3 f6 or 1.Nf3 f6 2.e3 e6.

Note: after 1.e3 e6 2.Nf3 black may prefer 2...Qf6; after 1.Nf3 f6 2.e3 black can play 2...d5.

- 1.e3 e6 2.Nh3 h6 or 1.Nh3 h6 2.e3 e6; 1.e3 e6 2.Nh3 f6 and 1.Nh3 f6 2.e3 e6.

Note: 1.Nh3 allows lines with 2.Nc3, whereas 1.e3 can let white choose lines with 2.Nf3.

- 1.Nf3 f6 2.e3 d5 3.Ne5 fxe5 or 1.Nf3 f6 2.e3 d5 3.Ng5 fxg5.

Note: after 3.Ne5 Bg4 white can play 4.Nxg4.

- 1.Nf3 f6 2.e3 e6 3.Nd4 Nh6 and 1.Nf3 f6 2.Nd4 Nh6 3.e3 e6.

Note: the order 1.Nf3 f6 2.e3 e6 3.Nd4 Nh6 let more possibilities for black (2...d5; 3...f5 and 3...c6) but in the line 1.Nf3 f6 2.Nd4 Nh6 3.e3, 3...Ng4 is better. It is not clear which move order is optimal for white.