1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... f8b4  4. c1d2  4... c7c5 [%c_effect c5;square;c5;type;Interesting;persistent;true] This is an interesting variation of the Bogo-Indian Defense, a favorite of the legendary GM Viktor Korchnoi. I played this move many times during my career, but I must admit that my results were not as good as Korchnoi's and Nakamura's, which is not so surprising, to be honest. 5. d2b4  5... c5b4 It seems strange that Black accepts to keep doubled pawns. After all, isn't this a weakness from a strategic point of view $2 I believe that \"doubled pawns\" is one of the most misunderstood topics in chess, but this philosophical conversation needs to be continued on another occasion. As compensation, the pawn on b4 causes some discomfort in White's position, gaining space and restricting his play on the queenside. It's not surprising that in many cases White plays a2-a3 at some point, voluntarily giving up this so-called strategic advantage. 6. g2g3 