Best response to the Queen's Gambit Declined: Traditional Variation (D30)

1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. Bg5 · Black to move

What is the best response to the Queen's Gambit Declined: Traditional Variation (1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. Bg5)? Black to move. See the top replies ranked by opening theory and real-game results, starting with Bb4.

The main theoretical reply is Bb4, reaching the Queen's Gambit Declined: Vienna Variation.