difference between fork and double attack

[henkvj]

For tags I can choose both 'fork' and 'double attack. Is there a difference between them?

[drahacikfm]

henkvj:  Check out this long discussion of the meaning of all the tags, in the Site Feedback part of the forum under "New tag suggestion":

http://chesstempo.com/chess-forum/site_feedback/new_tag_suggestion-t250.0.html

In short, a fork is a double attack, so you could put both tags if it's a fork.  Not all double attacks are forks, though.

[phogg]

It is my understanding that a fork is a double attack with one attacker, e.g., a knight or a pawn fork.

If a double attack involves more than one attacker, such as what may happen if you attack with one piece and in so doing open up a discovered attack on a second target, then it istn't a fork and should just be tagged as a double attack.

[richard]

phogg:  Unfortunately different people have very different definitions of these two.  Many users (and chess writers in general) see them as synonymous, others see forks as a subset of double attacks where only knights and possibly pawn forks are called forks , but all other attacks by a single piece on two other pieces are called double attacks.

I keep promising to create a description page which outlines how each tag should be interpreted on this site (to avoid the ambiguity in several of the current tags), as well as start discussion around a planned re-organising of the tags where some will be either merged or removed. I have a set of at least 5 or 6 new tags for adding, but wanted to get the descriptions up first.  Currently the descriptions are about 80% done, but they've been 80% done for a couple of months now :-)  I have a few other things on the plate right now so it is unlikely I'll get the descriptions done in the net few weeks either.

Regards,
Richard.

[phogg]

richard: The way I look at it, if you think of a fork like a fork in the road, you have a single point where the road diverges and two possible destinations. A fork attack follows this pattern, and it shouldn't matter what chessman is involved.

If a double-attack means a simultaenous attack on two chessmen, we know that forks are only one way in which it can be done, which rules out a fork being synonimous with double-attack. A fork attack is only one kind of double-attack.

[richard]

phogg: I tend to agree with you, the problem is that everyone has different definitions, this is why some canonical "Chess Tempo" definition of all the tags is so needed, i.e. "this might mean x,y or z elsewhere, but here it definitely means z".  For forks and double attacks I'm likely to merge them and create a new tag for the form of double attack you referred to.  There are a few double attacks tags that of the variety of those created by discovered attacks but the vast majority of them are just forks (by your definition of fork :-) ).

Regards,
Richard.

[phogg]

It just occured to me that there is also such a thing as a triple attack, where you move a piece into a fork attack onto two targets, with that movement also opening a discovered attack onto a third target.

Come to think of it, if the piece involved in the discovered attack was already attacking something in a different direction, with one move you could in fact convert the single attack into a quadruple.

[phogg]

I just played a game where I used a knight to fork two pawns and a rook. This example implies that a fork isn't a subset of the double attack tactic after all. I think a fork should be defined as a simultaneous attack by one attacker on two or more possible targets.

[richard]

Phogg,

Yes, there are all manner of corner cases with the tags, but the quadruple attack is not one of the tagging issues that keep me up at night :-)  The hundreds of knight forks that are tagged with double attack isn't either, but it doesn't worry me :-)

Regards,
Richard.

[dougy]

A triple attack is three simultaneous double attacks.  Eg. forking pieces A, B and C can count as a double attack on A and B, on B and C and on A and C.  By extension, an n-fold attack is (n choose 2) simultaneous double attacks.  (:

[phogg]

Maybe there should be a "multiple simultaneous attack" category, with a "fork attack" as one way in which it can be accomplished.

[drahacikfm]

Hey, if you capture en passant you could discover attacks on three diagonals and one file and your pawn could fork two things!  Sextuple attack!

I think if we worry too much about all these things we will never win a chess game

[revenant]

A "sextuple" attack?  Hmm...

http://en.wikipedia.org/wiki/Maenad

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