Originally posted by vipiuYes, that is correct. Took me fifteen minutes even though I knew there was a forced win (the notes to the game said so).
something like: N fork B takes, B sack+, KxB, p push=Q+ RxQ and black Q is hanging ?
Here is a link:
http://www.chessgames.com/perl/chessgame?gid=1473050
I believe White's rating was 2300+ at the time.
Originally posted by Fat LadySomething I find interesting is: for those who can solve this, how do they do it? Especially in cases of real games where there is no prompt to highlight that a combination exists. I didn’t solve it.
Yes, that is correct. Took me fifteen minutes even though I knew there was a forced win (the notes to the game said so).
Here is a link:
http://www.chessgames.com/perl/chessgame?gid=1473050
I believe White's rating was 2300+ at the time.
On initially looking at the position, I guess most experienced players identify many combinational motives/themes. e.g. a knight fork at f6; the bishop targeting f7, either to sac, or pin the pawn and therefore remove its defence of g6; a queen sac on g5, maybe to open the h-file for the rook; etc. I saw such potential “pieces of the puzzle” but I didn’t see the deeper idea of Black’s rook being deflected away from defending the queen. But I don’t think that was my main failing.
It is significant to note just how forcing the combination is…
Nf6+ A very forcing check.
… Bxf6
Bxf7+ Another very forcing check. Plus it’s a capture.
… Kxf7
g8/Q+ And yet another check that leaves Black’s options limited.
… Rxg8
Qxe4 Finally a capture
Consider how many legal moves Black had in the above line compared to White… very little. Of course, this is not to suggest that forcing moves are always good – they’re not – but in such positions, identifying them and calculating them definitely seems to be a big consideration. I think this is the main reason I failed to find the combination. I need to pay more attention to the advice of considering all checks, captures and threats (within reason).
As an aside, computers often use a technique of “quiescent search” where they don’t terminate/evaluate a line unless there are no captures or checks left in the final position. If this involves a large number of positions then humans cannot and should not attempt to emulate it. But some positions are feasible. For checks, the example position doesn’t present too many ways of initially keeping Black in check.
In some ways such thinking may tend towards “brute force” rather than tactical vision. i.e. you discover the idea by looking at forcing lines rather than considering a line because an idea suggested it. I think both approaches need to be used appropriately depending on the position.
Originally posted by VarenkaI think the problem is that it requires two sacs to work. we all spot the knight fork, and maybe even glance at the knight sac, but the bishop sac doesn't even register because wood is sacced already. our tactical mind simply hits an 'end of branch' condition and skips over to other possibilities.
Something I find interesting is: for those who can solve this, how do they do it? Especially in cases of real games where there is no prompt to highlight that a combination exists. I didn’t solve it.
On initially looking at the position, I guess most experienced players identify many combinational motives/themes. e.g. a knight fork at f6; the bishop t ...[text shortened]... suggested it. I think both approaches need to be used appropriately depending on the position.
a solution? I guess we just need to see enough of these to add the possibility into the tactical machinery. tweak the inner condition for stopping the search. -I doubt any specific observations like 'weak f7' will make a real life difference. at least the way I solve tactics it won't, which is mostly intuitive mental piece shuffling along the lines of 'that looks dangerous' instead of scientific weakness analysis.
oh, and I wasn't even close to solving it...
Well, I "saw" the solution (without realizing it) just by looking at the forcing moves. I have read something about the "psychological barrier" earlier somewhere, but in case the second sacrifice is forcing its will upon the opponent too, why not throw it on him as well?
Investigating a line until the forcing moves wear out should work OK in this position - that is if you're sharp enough to notice you can capture the Queen on the end of the road.
Perhaps the trouble here was that, as I mentioned above, there are several semi-forcing lines involving sacrifices but none of them (seem to) work. You tend to skip your thoughts to the next available source in case a sequence seems to run out of power.
And for solving this/such a problem, one should just set it up instead of looking at it digitally and play out the possible lines. I did not but would have done that, if the answer had not already been revealed. Then you notice such a thing as a hanging Queen earlier as well.
Originally posted by heinzkatit took about 3-5 minutes probably to me, and I started with the "obvious" 1 Qxg5...2 Nxf6...it was too easy(for fatlady) and it was not working...
The position is quite tactically suspect with so many "promising" tries available.
so... change the order of the moves is the main advice in tactic problems...
1 Nf6+ (looks like a nice not to do move, so for a tough chess problem it is important to be analysed carefully) so I insisted on it...plus that I usually go fast too deep into the solving branch, instead of going wide (I am trying to go wider in my games, and less deep)
by the way, I am sure I would have not found this in a normal long game...
Originally posted by vipiuYou're being far too modest. If you can find the sacrifices in Game 3967407, then this problem is child's play.
by the way, I am sure I would have not found this in a normal long game...
All too often, it is the forcing moves that are the key to combinations. The knight and Bishop moves force certain responses. Look at these moves first because there is less analysis involved, since the enemy has fewer responses. Also, you can look for a goal and work backwards (Like, how can I remove the rook from defending the queen). Always be scanning for potential moves while your opponent is moving.