Chess Opening Theory/1. d4/1...Nf6/2. c4/2...Nc6/3. Nc3

=Black Knights Tango=

3. Nc3
White add pressure to d5 and supports a possible later e4. The downside is Black can free the e-pawn and pin the White Knight by playing Bb4.

Theory table
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'''1. d4 Nf6 2. c4 Nc6 3. Nc3'''