Saturday, December 30, 2006

 

"Which Tactic is This?" Revisited.


Problem 540 from 1001 Brilliant Ways to Checkmate by Fred Reinfeld
White to Move
2k1q3/p2r1p2/P7/Q6B/8/Kp2r3/8/6R1 w - - 0 1


Note: if you want to solve this checkmate problem first, better stop reading now!


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I was stuck on this one for awhile and still did not get it right. The two easier variations are 1.Rc1+ Rc7?? and 1.Rc1+ Rc3. I won't comment on those - they are much more forced. I never could get through the 1.Rc1+ Kb8 variation completely on my own. After looking up the answer and working through it in subsequent circles, I began to appreciate this problem more.



Seeing that White's Queen could give check on b4 was alot different than giving check b5 was pretty easy. The key to the difficulty seems to be the c8 square. First it's where Black's King is, then Black is guarding c8 more times than it is attacked, then Black is guarding c8 once as it is being attacked once. At the same time the Black King is stuck in the corner, walking into a strange sort of back rank checkmate threat.


After 1.Rc1+ Kb8 2.Qb4+ Ka8 3.Bf3!+ Rxf3



I am now beginning to think I left something out of my Simultaneous Advantage post: tying down defenders. That is similar to immobilizing defenders, although they still have some movement available to them. Here is a simplified analysis of the above position.


Preexisting advantages:



On Qe4! Black gets some advantages from the move:

White gets advantages which are terminal for Black:

Defensive options:

Rook (on d7) to b7 walks into mate in one.
...Rb7 Qxb7#
Rook (on d7) to d5 walks into mate in two.
...Rd5 Qxe8+ Rd8 Qxd8#
Similarly Kb7 walks into mate in two.
...Kb7 Qxe8+ Rd8 Qxd8#
Queen takes Queen on e4 walks into the back rank mate in one.
...Qxe4 5. Rc8#



So what tactic (besides the fork aspect) is going on in the move Qe4? It seems to me as a special case of attacking the defender: a enprise attack on a tied down defender. Although Black's Queen is hanging, I believe a tied down defender essentially is equivalent to a hanging piece. Here's an example:



White to Move



Qb7! forks both Black Queens. Although they defend each other, the Black Queens cannot simultaneously defend against the back-rank mate threat and capture White's Queen.

-=-=-=-=-

I am getting a bit annoyed with this new blogger editor as it keeps adding lines, especially in bulleted sentences.**rolls eyes**. Perhaps WordPress is in my future...

Finished circle 4, and picking up some speed.

Happy New Year Everyone!


Comments:
It all looks so great!RS Gold
 
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