Thursday, January 29, 2015

Solving Chess Tactics -- the Logic of Forced Variations (or, only calculate what matters)

In my original blog series on calculation I recommended ways to more efficiently calculate forced variations using the broadly-recommended approach of calculating ALL "checks, captures, and threats".  My original blog series discussed the overall process of calculation (candidate identification, line calculation, and evaluation), with an emphasis on ways to more efficiently calculate specific lines (the second step) such as looking at your most forcing moves first, and searching for your opponent's refutations first.  Many of those ideas are here.

Calculating all checks, captures, and threats all the time is extremely tedious, and in writing that blog series I felt there was something missing.  And I have finally figured out what that something was -- I call it the "logic of forced variations".

This is an extremely simple idea but one I see strong players fail to appreciate (and I have seen annotators give exclams for moves that fall into one of these basic ideas):

When there is a threat on the board, you only need to calculate the five ideas that deal with that threat (capture, block, move, defend, and counterattack).  You do not need to calculate every check, capture, and threat on the board.

Also, if your move creates a threat, you do not need to calculate every check, capture, and threat your opponent can make.  You only need to calculate replies that address your threat.  If your opponent simply ignores your threat, that puts you one step closer to winning the point.

Simple, right?  This is all you ever need to know to efficiently calculate any forced variation.

Ok, maybe a few more details would help.

Let's start with a very simple idea.  The most forcing move possible in chess is a check, and everyone knows there are three (and only three) ways to deal with a regular check:  capture the piece, block the piece, or move your king.  The rules of the game require you to only make one of those three moves.  If you can't, the game is over.

However, if your opponent attacks your queen, the rules of the game do not require you to deal with it.  You can deliver checks, capture pieces, and threaten things, completely ignoring the attack.  It is completely legal to make a move that does not address a threat to your queen.  Yes, you will lose your queen, but the game does not end there (you should probably resign though!).  However, assuming you see the threat you will probably want to do something about it, and those same three move ideas -- capture, block, move -- apply equally here as well, with a few very important additions:  defend, and counterattack.

I have written about this in other blogs (see here, and here), but have done more Stoyko exercises using this approach and I have confirmed for myself that I have not missed any answers due to exclusion (not even considering a candidate idea).  When I did miss moves it was because I didn't "see" the possible move, even though I looked for it.

The basic process is this -- every time your opponent makes a move, or you make a move that threatens something, you:

(1) Find the threat -- actually, find ALL threats -- that the move created.  You must do this every single move, period.  The one time you don't do it, is when you miss your opponent's obvious mate in 1.  Prioritize the list of all threats, and be very specific about what the threat is (eg, "he's threatening to play Rook to a8 mate", and not just "he's threatening mate").

If you can't find any threats, then do not continue with these steps.  This only applies to forced variations, meaning there must be a threat on the board.

If you miss a threat because you looked but didn't see it, go train those types of patterns until you always see it.  If you miss a threat because you didn't look...then look next time.

(2) Make sure it is an actual threat.  Allow the threat to play out in your mind.  Does the threat actually win anything?  If so, what specifically?  Is there some tactic at the end that makes it not work?  Can you make a move that, if the threat is carried out, would undermine the threat?  Add that move to your candidate list.  The "threat" could actually be a mistake, so start by looking at that.

(3) Now that you have found a threat that is both real and specific, you have to deal with it.  Here are the five options you have to deal with the threat:

- capture:  or somehow deal with one/any of the attackers (like a pin to something more valuable, or deflection);
- block: move piece to block the threat, or reposition a piece to block on the next move;
- move: simply move your piece somewhere else, or create space for your piece to escape to (or to allow a piece to block) on the next move;
- defend: simply add a defender to the attacked piece/square
- counter-attack: this can have three distinct goals:
- counter-attack to WIN: a move that creates a new threat that is at least equal to, but hopefully greater than, the threat against you,
- counter-attack to DRAW: a forced series of moves that draws through repetition, or stalemate
- counter-attack to DEFEND: a forced series of moves that allows you to employ any of the four basic defenses above (capture, block, move, defend).  This could simply be giving a queen check that allows you to reposition the queen to defend a square, or say attacking a queen with a rook in order to reposition the rook to block another threat.

(4) Search for all moves that accomplish each of the above candidate ideas.  This will give you a thorough and complete list of candidate moves.  This covers every single conceivable reply possible.  You might not actually "see" the candidate move, even at 1 ply, but just looking for it is the key.

If you don't find a candidate move, but you did look for it, then train the pattern that you missed until you never miss it again.  If you don't even look for the candidate moves, then you'll never find them!  Look next time.

(5) Work through each of the defensive replies, playing out each move one at a time, until you find the move that results in something good for you...or the least bad option.

That's it!  Try this the next time you run through a set of tactical positions.  This process will NOT help you identify vulnerabilities or find possible tactics.  But if you do see a threat on the board, you now know how to work through it...and if you find a way to threaten your opponent, you now know the full range of replies you need to calculate...which is not every single check, capture, threat possible.

For future blog posts I plan on exploring each concept in more detail.  For example, blocking an attack results in a pin, defending results in possible remove the guard tactics, and counter-attacking is what world champions do...


  1. Hello Danny!

    I have just started reading your blog. There are VERY interesting topics you explain quite deep. However what I miss the most is the example - the concrete diagram with some explanation (and simple variations).

    If you would provide a diagram with some variations - and explained it as you do it now - it would be much easier fo find a refutation or confirmation. For now it is "too abstract" to me, even if I feel you are right with your findings.

    Anyway - keep up great work and share your ideas as much as you can! :)

  2. Hi Tomasz -- I am very glad that you enjoy my blog, and I would be happy to add diagrams that highlight the concepts. I'm still learning how different blog tools work and have been looking for one that allows you to include actual variations you can click through, but I'm not happy with the ones I've seen out there. So for now I'll stick with static images.

    Is there a particular topic you are interested in most? I have lots of ideas for this blog, but would be happy to focus on any particular issue. For example, I could take one single position and break it down in detail this way, or use different positions for different topics...or both!

    My next ideas are (1) to explore the implications of each type of defensive option in much more detail (eg, defending can hold your material, but can also lead to basic remove-the-guard tactics; blocking an attack results in a pin...or is a pin really a discovered attack in disguise?; etc); and, (2) an in depth look at pawn breakthroughs in the endgame (not just the classic 3v3, but really digging into how it works).

    For now though, I'll go back and add some positions to demonstrate these defensive themes, and if there are any issues you want to explore more deeply, just let me know.

    Thanks again for your comment, and thank you for reading my blog!

  3. The other topic I plan on writing about is the importance of time/tempo in a threat.

  4. Thanks for your reply :)

    I am especially interested at such topics as: threat(s), fortress, draw zone, compensation (sufficient and insufficient). However I will be glad if you show the examples with the help of diagrams and/or variations. It really does not matter if it is a single position explained in details or the group of position (a specific concept) divided into the more specific ones.

    1. Will do -- I've already compiled some simple positions to show each theme. I'll add more complicated ones later. New post coming very soon!

  5. I've started to post some specific examples of the various defensive ideas, and the calculation process. I hope you like!!

  6. Oh yeah - I have been waiting for these posts and I am going to read them very carefully! I will make some comments to these posts! Thanks for your support and posting about the subjects that are very interesting to me! :)

    Keep up great things my friend :)

  7. Your posts are very inspiring to me. They give me the boost to uncork the threads and subjects I have been waiting for "better time" (i.e. delaying as much as possible). Despite it I am really grateful for these as they contain so many great and broad ideas and concepts that I can "swim in these" as in the ocean.
    It is a real pleasure to digest your posts! Every time I read these - there are new ideas they are creeping into my mind all the time. Maybe you will be a bit surpised, but I could call you "an improved Dan Heisman" ;) :). You are writing quite amazing chess context with a very nice explanation and presentation.

    BTW. I have copied your post into Word and converted them into PDF format. This way I can digest these without the need to fire up the browser ;) :)

    1. Thanks, Tomasz! That is quite a compliment!! I have several more posts coming soon to finish up this series on calculating forcing variations...and I will certainly include a table to summarize the basic calculation process as well as the five core ideas.