Puzzle of the week #64

We are going to celebrate the milestone 64th puzzle with a straight attack to the King. The original author is a very important chess figure, still very much active in international tournaments at the respectable age of 78. I am talking about Viktor Korchnoi, the oldest active GM. A lot of people know him from his 2 World title matches vs Karpov in a time (mid seventies) when his defection from USSR and becoming a citizen of Switzerland was front news. However of true importance should be the gems he created on the chess board. Example: he is recognized as the World's specialist in English opening, his new ideas pushing this opening and chess in general to a new level.
The above position is from one of his games: Viktor Korchnoi - Andrey Peterson, 1965 Kiev. Here he decides to start the attack against the enemy King by sacrificing his Bishop: 28.Bxh6 ... Your tasks:
a) Continue the attack and win the game like Viktor did (10 points)
b) Explain why he decides to start the attack at this moment (10 points)
Total available points for this puzzle is 20. The answers will be published next week together with puzzle #65.

Puzzle #63 solution:
Solutions from last week: I have chosen the most complete one, plus the original. Joshua:
a) White's Positives:
1. The Queen is attacking the Black King and is pinning the Black Knight on e6 to the King.
2. The Bishop on g2 covers the biggest diagonal from a8 to h1 and threatens the Black Rook on a8.
White's Negatives:
1. Even though the Knight on e7 is directly attacking the Black King, it can be captured in one move.
2. The White King is not safe at all. The f2-pawn blocks the e1 and g1 squares so that the White King cannot move.
3. The Rook on a1 and Knight on b1 are not in play.
Black's Positives:
1. Has passed pawn on f-file on the 7th rank and is protected by the Rook on f8.
2. Even though the Black King in check, he is safe because the White Knight on e7 can be captured in one move or the Black King simply move away to h8.
3. The Black Queen is on a good square, e8, where she can crash down on the White King and mate when Ne6-Nd4 then Qe8-Qe2#.
4. The Black Bishop on c8 can move to h3 to check or checkmate the White King once the Black Ne6-Nd4 and the White Bishop moves away.
Black's Negatives: 1. Black's Rook on a8 can be captured in one move, i.e., BxR. Black is better because he has many different attacking pieces. For example, he has a protected passed pawn on the f-file that traps the White King from moving away, i.e., e1 or g1. The Black Queen is in a good position on e8 and can crash down on the White King supported by Black's Knight on e6, once it moves to d4. Also, Black's Bishop on c8 can shoot to h3, attacking the White King, once the Black Knight on e6 moves to d4, and White's Bishop on g2 moves away.
b) See solution with Tim Krabbe annotations:
[Event "Puzzle #63"][Date "2009.03.20"][Result "0-1"][SetUp "1"][FEN "r1b1qrk1/p1p1N1pp/4n3/8/8/1Q1P2P1/PP2PpBP/RN3K2 b - - 0 17"]17...Kh8 {Wasting no time, all Black wants is to unpin his own Knight, which gives him a winning attack} (17...Qxe7 18.Bxa8 Kh8 {White's combination would still have been dubious}) 18.Qb4 (18.Bxa8 Nd4) 18...c5 19.Qh4 Rb8 20.Be4 Ng5! 21.Ng6+ Qxg6 22.Bxg6 Bh3+ 23.Qxh3 Nxh3 24.Be4 Rxb2 {and Black won quickly}

Correct solutions:
John, Karl, Andy Y - 20 points
Andy Q, Joshua, James, Jeremy - 19 points
Wilson - 12 points
Mark - 10 points
Humphrey - 7 points

Standings:
John - 255 points
Joshua - 246 points
Andy Qian - 236 points
Jeremy, Mark - 223 points
Karl - 200 points
Andy Yee - 191 points
James - 138 points
Wilson - 122 points
Humphrey - 111 points
Marcus - 89 points
Jacky - 80 points
Katerina - 72 points
Nathaniel - 42 points
Joanne - 21 points
Darren - 20 points