Thursday, November 15, 2007

Is a pin a tactic?












At the moment I'm investigating duplo-moves. There are 3 of them:
  • Double attack.
  • Discovered attack.
  • Pin/skewer.
I'm focussing on double attacks and haven't thought about the other two yet. So far I haven't reached conclusions worth mentioning. A discussion at Blue Devil's site caused me to write a little attribution about pins.

Everybody seems to use his own definition of tactics. That is not very handy. Definitions are meant to make communication easier, not more difficult. A definition in itself is not true or false. It is a consent between people and a matter of preference. I use the following definition:

A tactic gains wood in a forced way.

I consider the king as wood and mate as a trap.
According to this definition, not every duplo-attack is a tactic. Take for instance the following double attack:






















Black to move.

White has just made the duplo-attack Qg4. It attacks the two targets knight g6 and bishop b4. We don't call this a tactic. We even don't call this a double attack. So I think it is a good idea to call it not a duplo-attack either.

The reason for this is twofold:
  • One of the targets is well protected.
  • The value of that one target is lower than the value of the attacker.
The same is true for the pin. There is no difference between a pin and a skewer other than the difference in value between the two targets. This meets usually the second point of the list above: The value of that one target is lower than the value of the attacker. If the first point of the list is met too, that is to say the pinned piece is well defended, then there is no tactic nor a duplo-attack.

In the following diagram you see a pin that is both a tactic and hence rook c1 is a duplo-move:





















Black to move.

Despite the fact that the value of the knight is lower than the rook, it is still vulnerable to the duplo-attack Rc1. Because it is insufficient defended. Rook c1 truly attacks two targets simultaneously. Black needs two mono-moves to escape from both attacks.

9 comments:

  1. "I consider the king as wood and mate as a trap."

    Excellent way to accommodate the King into the defintion. Quite nice, especially mate as trap.

    I think this definition of tactic is the most clear. From other definitions I have seen it isn't as clear (though Heisman's 'science of piece safety' is nice).

    And then to deal with putative counterexamples such as were brought up yesterday, you can say, yes those are tactical constraints on the position, by which I mean if you do X (move out of pin) you will lose wood. So the constraints exist because of the potential tactic, not because there is a tactic in a pin.

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  2. There is no tactic as long as the pin is still in the hand grenade.

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  3. 1. A tactic gains wood in a forced way.

    add in more types of tangible gain -->

    2. A tactic gains a tangible advantage in a forced way.
    (includes force stalemate in an otherwise lost position)

    add in intangible gain -->

    3. A tactic gains an advantage in a forced way.
    (includes gain control of a key square, etc.)

    use the proper term :) -->

    4. A combination gains an advantage in a forced way.
    (includes gain control of a key square, etc.)

    the full Yuri -->

    5. A combination is "a rearrangement of the connection of pieces of both sides, which forces a co-ordinated connection of contacts, which is advantageous to one side." [Chess Tactics for Advanced Players by Yuri Averbakh].

    A pin is not a tactic (nor a combination). Like a hand grenade, it is a weapon.

    Deciding to supply your soldiers with hand grenades is strategic. Using a hand grenade is tactical. Using a hand grenade to force an advantage is a combination.

    And yes, these are just words. But a tactic which is a combination is commonly called a ... combination. All combinations are tactics, but not all tactics are combinations.

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  4. Glenn,
    2. A tactic gains a tangible advantage in a forced way.

    Be carefull! Before you know it you have broadened the definition of tactics beyond practicality:)
    The field of activity of tactics is the gain of wood. Tangible or intangible advantages are a side effect of avoiding the loss of wood. Those are called "positional advantages". A positional advantage enhances the chance for future tactical gain. Solely.

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  5. Glenn: forced stalemate tactics are a good putative counterexample to the wood-gaining definition of tactics.

    For tactics you say: A tactic gains a tangible advantage in a forced way.

    I think this is pretty good, as long as it includes 'forced' (which implies that significant material or mating considerations are in play).

    For beginners I think the wood-grabbing definition is OK.

    However, your quoted definition of a combination is awful. It's not clear what the terms mean (e.g., 'connecting pieces'), much less what the sentence means. To quote that as if it has some authority is a mistake: you'd need a whole post to explain what the hell he is talking about in that definition. Then we could argue about whether the definition is good or not.

    I just think of a combination as a tactic that involves more than one basic tactical motif (i.e., a combination of motifs). An asset is that it leaves open to you to define what a tactic is.

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  6. To clarify my earlier comment, I would choose #4:
    4. A combination gains an advantage in a forced way.

    This is similar to the "full Yuri" without requiring the background.

    I think that the word you are actually looking for is combination (not tactics).

    "Tactics is the art of using troops in battle; strategy is the art of using battles to win the war."
    -Carl von Clausewitz

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  7. Your first example reminds me of positions that my students will comment on by saying "I'm forking the bishop and the knight." I then explain that yes the queen is attacking two pieces, but one is guarded and the other can move away.

    I like the simply explanation that's in the glossary of Weeramantry's Best Lessons on a Chess Coach.

    Tactic: A mode of action charecterized by use of threats towin material or mate the opposing king.

    Stratagy: Formulation and execution of a long-term plan designed to improve one's position.

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  8. Polly,
    yes, that's how I like definitions. Clean, simple and practical. Not necessarily scientificly correct.

    Tactic: A mode of action charecterized by use of threats towin material or mate the opposing king.

    Because of a discussion of terms with Christian I started to use the word "attack" in stead of "threat". But in the example in my post that you mention both the bishop and the knight are under attack though only the bishop is threatened. So I must reintroduce the duplo-threat again in stead of the duplo-attack.

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  9. In chess, there is strategy and tactics. Strategy involves long-term concepts, while tactics are immediate. Strategy is academic and theoretical; tactics are practical and concrete. You can win without strategy. If you do not apply effective tactics on every move, you will not survive long.
    Grandmaster Rashid Ziatdinov

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