411 REFERENCE · Wikibooks
Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nc3/3...Nf6/4. Nf3/4...e6/5. Bg5/5...h6/6. Bh4/6...dxc4/7. e4/7...g5/8. Bg3
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Anti-Moscow Anti-Moscow D43
8. Bg3
White retreats their bishop to g3.
Black's pawn on c4 is still hanging, so they should defend it with /8...b5/.
Theory table
all 8. ... b5
References
Semi-Slav Defence Anti-Moscow_Variation:_5...h6_6.Bh4_dxc4