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

Jan 29, 2015, 10:17 AM |

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.  It doesn't take long for a player to learn that he/she needs to run through all three candidate moves when looking at any check.

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, 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:

  1. capture:  or somehow deal with one/any of the attackers (like a pin to something more valuable, or deflection);
  2. block: move a piece to block the threat, or reposition a piece to block on the next move;
  3. 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;
  4. defend: simply add a defender to the attacked piece/square
  5. 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.  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. 

And 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...