If 46. Ra6, h2; 47. b6, h1(Q); 48. b7, Qg2+ and Black mates in a few moves. Whereas if 46. Rc6, h2; 47. RxRc3, h1(Q); 48. Rd3, the position is much less clear.

Threatening 49. Ra6+, K to the b-file; 50. b7-b8(Q)+ and Black is finished.

This could be drawn, but the defending side must know how. He must keep his king on or near the queening square, and he should avoid exchanging rooks.

A critical check: obviously the White king must not go the 3d rank, otherwise ... Rb3+ wins the White rook. So the White king must retreat--this gains a tempo for Black.

Ah, how tempting--to threaten the rook! But a slight mistake, as it moves the White king away from the queening square.

Preparing to advance d4, where the d-pawn will be covered by the rook.

Another slight inaccuracy; Kd2 was called for. The White king should stay on the queening file, if at all possible.

?? A fatal mistake this time. The king should go towards the queening square, i.e., 52. Kd2, and the rook should be maneuvered to h8 from where it can check the Black king from behind.

! The White rook is now double attacked, and it cannot move away; White is forced to exchange rooks, and Black re-takes gaining the opposition. The game is now a forced win for Black.

White must relinquish the queening square: e.g., 55. Kd1, Kd3; 56. Ke1, Kc2; ... or 56. Kc1, Ke2; .. either way, the d-pawn is home safe. It moved only once, on move 2, but it decides the game! 0-1