19....N6e720.Bxb5...In the endgame, a Rook and two pawns are usuallystronger than two Knights.20....axb521.Nxb5Rda621...Rb722.Nxd6Nxd623.Rc522.Nxa7Rxa723.Rc5Nb623...Rxa324.Rxc724.Ra1Kf825.a4Ke826.a5Nc427.Ra2f528.Kf1Kd729.Ke2Nd6This allows theWhite pawns to move forward.29...c630.Kd3Nd631.f330.b5Nc4Black probably overlooked30...Nb731.Rxc7+Kxc732.b6+Kb833.bxa7+Kxa734.Rc231.Ra4Kd831...Rxa532.Rcxc431...Nxa532.Rc232.a6Nb633.Ra1Nec834.h3...Opening a "secondfront" - a standard technique.34....h535.g4hxg436.hxg4fxg437.Rg1Ne738.Rxg4Na439.Rh4c6It was probably better for Black to accept theexchange sacrifice but White should win anyway:39...Nxc540.dxc5Kd741.Rh8Nc642.Kd2Nb4(42...d443.e4)43.Rh7+Kd8(43...Ke644.Kc3Nxa645.bxa6Rxa646.Rxc7)44.Rh4Nc6(44...Nxa645.Ra4)45.Rh8+Kd746.Kc3wins for White.40.Rh8+Kc741.Rc2Nb642.Rh7Kb843.bxc6Rc744.Kf3Ka745.Ra2Nbc8