Chess Opening Theory/1. e4/1...Nf6/2. e5/2...Nd5/3. d4/3...d6/4. c4/4...Nb6

= Alekhine's Defence = Now that the knight has left the d-file, the threat of 5...dxe5 6.dxe5 Qxd1+ 7.Kxd1, shattering White's pawns and preventing castling, must be dealt with. White has two main choices now: the aggressive Four Pawns Attack (/5. f4/) and the subtle Exchange Variation (/5. exd6/).

Theory table
.

'''1.e4 Nf6 2.e5 Nd5 3.d4 d6 4. c4 Nb6'''