 White should have carried out his plan of winning Black's a-pawn, for example with 46.Qc1 (threatening 47.Nxb6+ cxb6 48.h4!gxh4 49.Qh1 and Qh3, winning) Qa7 47.Qd2 followed by Kb3, Nc3, Ka4, and Na2–c1–b3.46...cxb6 Now Black threatens 47...h4, locking down the entire board with his pawns, so White tries to break the position open.