Thursday, July 31, 2014

When in doubt, Bxh7 (Part 3)

If anyone still recalls one of the articles I wrote an incredibly long time ago regarding the attack against a castled king (http://nushsblackknights.blogspot.sg/2013/08/how-to-attack-part-2.html), we had discussed about the advantages and drawbacks of using the h7/h2 focal point for an attack. This square is very easily accessible to the attacker, but the difficulty lies in preventing the escape of the enemy king after the clearing of the square. This is especially true in the case of the Greek Gift sacrifice, since after Bxh7 (or Bxh2 for White) followed by Kxh7 the defender often has many squares for his king to run to (Kg8, Kh8, Kg6 and Kh6) and the attacker must know how to respond to all of them!

As such, it is important for us to know how to calculate the many variations that follow after the launch of the sacrifice, and hopefully we will be able to uncover the many details that explain why this tactical motif continues to mystify us even till this day.

Today, we will look at the variations where the defending king retreats back into his shelter (...Kg8/Kg1 or Kh8/Kh1). When this happens the resulting attack is often easy to execute since the attacker's Queen and Knight work together to make a formidable strike force. A look at the very first example from Part 1 can confirm this quickly:

Position after 7... O-O

And if you can recall, the variations after 8. Bxh7 Kxh7 9. Ng5+ Kg8/Kh8 ended quickly:

8... Kh8 9. Qh5+ Kg8 10. Qh7#

8... Kg8 9. Qh5 Qxg5 (in order to prevent mate on h7) and Black loses the Queen.

However, such a position can only occur in an attacker's dream, and in reality the differences in a position often make the subsequent variations after Kg8/Kh8 (Kg1/Kh1 if Black is the attacker) much more complex than they seem. In the following position from an Advance French variation, White seems to be facing problems since Black has a potential escape square on f8. But fortunately for White, other aspects of his position, such as the possibility of the rook lift to e3, help him create a successful mating attack:

White to move


1. Bxh7+! Kxh7

After 1... Kh8 White simply plays 2. Ng5 with 3. Qh5 to follow

2. Ng5+ Kg8

Or 2... Kg6 3. Qd3+ f5 (3... Kh6 4. Qh7#) 4. exf6+ Kxf6 5. Qf3+ after which Black will collapse very soon

3. Qh5 Nf8

Black cannot defend the f8 square; for example 3... Qe7 leads to 4. Qh7+ Kf8 5. Qh8#

4. Qxf7+ Kh8
5. Re3!
1-0

The rook lift decides matters; there is no stopping 6. Rh3+ followed by mate.

In the next example, Black (the attacker) also faces problems since White's bishop on c1 seems to be able to help defend the h2 square, thus making Qh4 seem impractical. But fortunately for Black, he has the additional option of Qe4+ and other active factors which allow his attack to succeed:

Black to move


1... Bxh2+
2. Kxh2 Ng4+
3. Kg1

3. Kh3 falls quickly to Nxf2+ winning the queen, while after 3. Kg3 Qe5+ 4. f4 Qh5 5. f5 Qh2+ 6. Kxg4 h5+ 7. Kg5 Qg3+ 8. Kxh5 g6+ 9. fxg6 Re5+ it is not hard to spot a checkmate for Black here.

But now what? Black cannot play 3... Qh4 since 4. Bf4! foils his plans immediately by bringing an extra defender to the h2 square. Fortunately, Black has a way to deny the enemy bishop access to the h2-b8 diagonal:

3... Qe5!
4. f4 Qh5
5. Rf2 Qh1+!
6. Kxh1 Nxf2+
0-1

It is interesting to note that in our previous two examples, the attacker's plans would not have succeeded if the pawn were on h5 (for the first position) or h4 (for the second position). For the former, this would have denied White the opportunity to utilize his rook lift effectively, while in the latter the same goes for Black's 4... Qh5.

And thus here are some of the interesting factors about the position which one has to consider before he can launch a successful sacrifice. In our next article, we will extend our discussion to the more complicated examples: When the defending king has the option of using the g6/g3 or h6/h3 squares as escape routes.

Links:
Part 1: http://nushsblackknights.blogspot.com/2014/07/when-in-doubt-bxh7-part-1.html
Part 2: http://nushsblackknights.blogspot.com/2014/07/when-in-doubt-bxh7-part-2.html

Sources:
"Art of Attack in Chess" by Vladimir Vukovic

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