Friday, April 13, 2007

Chess -- exhaustive list, mate threat

I like exhaustive lists (on an abstract level) for all kinds of situations in chess (and life). A simple one that most learn early on is how to deal with a check. The three ways: take the checking piece, block it, or move the king (in double check only the third option applies, and blocking isn't possible when a knight checks).

What would be an exhaustive list of possibilities prevent a threatening mate? I think it would be:

1. Take any of the pieces that threatens mate.
2. Block any of the mating pieces.
3. Arrange so that a piece will be able to block the mating piece (if it's not a knight).
4. Set a piece to guard the square that the mating piece is going to move to.
5. Prepare an escape route for the king (i.e. move a piece, for example the rook on f8 if the mate threat is Qh7+)
6. Make a check yourself (can be very disrupting in many positions).
7. Move the king

Does this cover it all? (Btw, I put no thought into the order, but I guess they should be arranged in order by some criteria.)

(Btw again, "the mating pieces" refer to all pieces that cooperate in the mate, and "the mating piece" refers to the one of those, if several, that does the actual mating, the check.)

I wrote the above from the perspective of the defender, but it is as useful for the attacker. When you consider making a move that threatens mate (or a move that threatens a move that threatens mate...), you need to be able to go through every possible way that mate can be diverted. And the further into the future the mate threat is, the more difficult it is to make sure you've gone through every relevant counter move, and having a series of steps like this does help.



DG said...

You might want to note that not all these options are available under all conditions. For example, a double check cannot be parried by capturing or blocking one the attacking pieces.

XY said...

Okay, that's true and I did mention that about double checks in regard to ordinary checks (and all mates include an ordinary check, so to speak).

I wanted a list that covers all possible circumstances. That some steps are unnecessary in some positions is easy to deal with ("Can I block that mating double check? No. On to the next step.")

Still, wouldn't have hurt to point out what you say (but I'll leave my post as it is now that it has been mentioned in the comments.)

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