1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1b5  3... a7a6  4. b5a4  4... g8f6  5. e1g1  5... f8e7  6. b1c3 As far as I know, this is the first time that Carlsen has played this move. It is not as popular as 6.Re1 or 6.d3, but many strong grandmasters have tried it. 6... b7b5 