Chess Opening Theory/1. e4/1...c6/2. c4/2...d5/3. exd5/3...cxd5/4. cxd5/4...Nf6

= Accelerated Panov Attack =

4…Nf6
The idea of the move Nf6 is to put another attacker on the d5 pawn, that way, white could not save the pawn and gain a tempo by attacking the queen.

Theory Table
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1.e4 c6 2.c4 d5