Chess Opening Theory/1. e4/1...Nf6/2. e5/2...Nd5/3. c4/3...Nb6

White may now play 4. d4 to sure up their centre. This is the main move and reaches positions familiar from the 3. d4 move order, where often White plays c4 as well. 4...d6 5. exd6 reaches the exchange variation; 4...d6 5. f4 transposes into the four pawns attack.

4. c5 stays in original territory. This is the Lasker variation. White chases the knight again but it usually returns to plant itself on the newly minted outpost on d5, 4...Nd5. 5. Nc3 e6 6. Nxd5 exd5 7. d4 to close up the outpost might be sensible, or the game may continue 4...Nd5 5. Bc4 e6 6. d4 b6 7. cxb6 axb6 =.

4. b3 is the Steiner variation.

'1.e4 Nf6 2.e5 Nd5 3.c4 Nb6'

Wikipedia has related information at Alekhine Defence.

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.