an interesting greek gift secrifice.. the hard move is actually move 17 (of the game, about move 5 in the puzzle)
the game is Colle- O'Hanlon Nice 1930
in the game black played the Kg6 and lost quickly.. in first analayze it came up that black could draw by playing Kg8.. after further analayze they found the 17th move, which gives white the win in all variations
b3 is wonderful... found it, but only because I saw yourbetteroffasian's kibitz. yes b3 is necessary... b3 gives White mating attacks using the White's Bishop access to the a3-f8 diagonal -- Black can't defend both the a3-f8 diagonal, and g7.