Queens Knight Defense
Unless the game transposes to another opening, the Encyclopedia of Chess Openings code for the Queen's Knight Defense is A40.
This opening was tried by some hypermodern players such as Aron Nimzowitsch and Efim Bogoljubov, but it has never become very popular. The move 1...Nc6 is a fairly committal move which blocks Black's c-pawn; usually Black delays playing it until White's setup is clear.
Most games featuring 1.d4 Nc6 transpose to another opening. After 2.e4 the Nimzowitsch Defense arises. After 2.Nf3 d5 a variation of theQueen's Pawn Game is possible. After 2.c4 d5 the opening is a Chigorin Defense.
There are some lines which are unique to 1.d4 Nc6, most importantly 2.d5 which chases the knight away, usually to e5. The opening resembles an Alekhine's Defence but on the opposite side of the board. In an opening book by Sid Pickard, this variation was called the Bozo–Indian Defense – "Bozo" being a combination of the prefixes "Nimzo" and "Bogo".
- 2.d5 Nb8 (Montevideo Retreat)
- 2.c4 e5 3.d5 Nd4 (Cannstatter Gambit)
- 2.c4 e5 3.d5 Nce7 (Lithuanian Variation)