Perusing a database of Tal's games, I played through this one and arrived at this point where white's game collapsed like a house of cards. Two great attacking players faced each other during the Soviet championships that year, and I could not resist investigating how their game panned out. As you can see, the ending involved bishops of opposite colors with black having a pawn advantage. Chess theory tells us that such endings are drawish even if one side has a material advantage in pawns. Also, we are told that the attacking side, in this case black, should place his pawns on squares that are opposite to the color of his bishop while the weaker side should strive to have his pawns on squares that are of the same color of his bishop. This is the theory, and the present position does not subsribe to it. Black's passed B pawn will require the attention of white's bishop while the king holds the fort on the kingside. Tal, in his eternal genius, dropped a bomb with 39... Bf3! I would love to have seen the look on Keres' face after this move. Keres had to recapture with 40. gf or else black will just play 2... Bg2 and win two pawns outright. Play continued 40... Kf3 41. Kf1, b5 42. Bd2 stopping the advance of this pawn. Black goes on 42... h4 43. Bb4, h3 and now the H pawn must be addressed. The white king goes 44. Kg1 and Black just lets the H pawn hang while he makes way for the advance of the F pawn which should promote without much trouble after 44... Ke2! White resigned. If 45. Kh2, then 45... f4 46. Kh3, f3 47. Kg3, f2 and the pawn will promote. White could also try 47. Bc5 but 47...b4 will stretch the bishop between two passed pawns, and one of them will promote. I would like to point out that after the bishop sacrifice on F3, Tal ended up with three passed pawns, and all of them have white queening squares.