Queen's Knight Defense
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The Queen's Knight Defense is a chess opening defined by the opening moves 1.d4 Nc6. The opening was tried by some hypermodern players such as Aron Nimzowitsch and Efim Bogoljubov but the opening has never become very popular. 1...Nc6 is a fairly committal move, blocking the c-pawn, and usually Black will delay 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 the Queen's Pawn Game can come. 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 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 mixture of the prefixes "Nimzo" and "Bogo".
Unless the game transposes to another opening, the Encyclopedia of Chess Openings code for the Queen's Knight Defense is A40.