Anglo-Slav Variation, London Defensive System

With 4...Bf5 Black places the light-squared bishop outside the c6–d5 chain before ...e6, in the manner of the London System with colors reversed, which gives the line its name. White normally continues 5. Bg2, the most common choice, or 5. Bb2, which has scored better for White; 5. d3 is rarer and has done poorly. The engine assesses the position as level, and results are close.