Monday, March 2, 2015

Calculating Forcing Moves: Defensive Idea 3, Part 1 (Move)

When your opponent creates a (real) threat, or you are considering creating one against your opponent, there are five defensive ideas to consider.  We have already looked at different ways to implement the first two defensive ideas:  Idea 1 (capture the attacking piece, pin the attacking piece, deflect the attacking piece), or Idea 2 (block the attacking piece).  This post will explore the third basic idea of moving out of the attack.

The idea is straight forward -- your piece is being threatened and you find other squares to move to where it is not threatened.  This usually happens when the piece being attacked is more valuable than the piece doing the attacking.  The search method is simply to look for squares the piece can move to, and add those to your candidate list to calculate further.

Moving your piece out of the attack is often the safest, least complicated, and easiest type of move to find and to calculate.  The simplicity of this idea gives us the opportunity to look at another aspect of piece safety and calculation, which is considering your opponent's response even in quiet looking positions.  We'll look at a simple position that demonstrates this very clearly.

But like everything in chess, there are complexities.  There are times when the piece being attacked has important defensive duties and shouldn't move, has nowhere to safely move to, or simply cannot legally move because it is pinned the king (or something more valuable).  This brings in several entire families of tactics -- pins, remove the guard, trapping, mating nets -- and those complexities are a topic for another blog series!

The other element of this idea I do want to explore in a future post is "preparing to move".  These moves are possible when the threat is one move away, and you have time to move another piece out of the way so that you can escape to, or through, that square when the threat is played.

Let's start out with a simple position to demonstrate the basic idea.  The general process is to evaluate the position, identify and prioritize all threats, and then to use the five defensive ideas to identify specific candidate moves.  Next, calculate each candidate move to the end and evaluate the final positions (material and activity).  As you progress through the candidates, keep in mind the "king of the hill" (KOTH) candidate move to help you pick the best at the end.

White just played Kd4 attacking Black's rook.  Black to move.

6k1/6p1/6Np/p1r2P2/P2K4/2P5/8/8 b - - 0 1

Let's evaluate the position and then find all of white's threats.  Black is up the exchange, but white has an advanced passed pawn and his knight and king are more active than black's pieces.  Black is playing for a win and has the simple plan of trading his rook for white's knight and a pawn, while white is playing for a draw and has reasonable drawing chances.  White's immediate threat is to capture black's rook with Kxc5  He has no other threats.  Let's look at the five defensive ideas to see what candidate moves we find, and then pick the best move.

Idea 1 (capture, pin, deflect):  none.
Idea 2 (block):  none.
Idea 3 (move):  the rook has nine legal moves several of which are clearly unsafe, but a few look interesting: Rxf5, Rc6, Rc7, and Rc8.
Idea 4 (defend):  black cannot add a defender to the rook.
Idea 5 (counterattack with an equal or greater threat to WIN, DRAW, DEFEND):  an equal threat would be to attack a rook or to return some his material for some other concrete advantage, but neither idea is possible here.  A greater threat would be to attack the king, but neither check is safe for black.

This was probably the easiest list of candidate moves to find so far!  So let's start with the most forcing reply first: 1...Rxf5:

Black has now won a pawn and has connected passed pawn on the kingside and will certainly win...that is, unless white can find a refutation.  This position is now the kind of thing you'd see in Bain's tactics book, and would make a wonderful tactical puzzle for beginners.  What kind of thought process could help beginners find white's refutation?  Well, first of all the right approach is just asking yourself -- before you touch the rook -- "is 1...Rxf5 safe?"  You should ask that question every single time you are about to make a move, especially a move that doesn't create a specific threat.  Certain visual patterns give you ideas to help find offensive moves (the topic of yet another future blog series), and in this position hopefully everyone can see the knight fork 2. Ne7+ which refutes black's move.  There are three visual clues that could lead one to immediately find the fork:  the proximity of the knight to the black's pieces, the specific colors (knights fork targets that are on the color they are currently standing on), or the specific geometry of the location of the targets (in this case one square away on a file/rank, or on the adjacent diagonal squares).

So even though our four candidate moves were rather simple to find, the thought process of searching for your opponent's most forcing reply should be engrained in all beginners.  That one single question alone, plus lots of tactical training, should allow you to find white's refutation and hopefully avoid making complete blunders.  Here again I would make the same point I have made before...if you stop and look for refutations but miss certain patterns, you should go train those patterns until you don't miss them anymore.  But the key is to ask the question.

We can very quickly see that of black's four candidate moves, only one of them (1...Rc7) avoids the knight fork.  After doing the same satefy check as above, you can see that the rook is totally safe on c7, and the game continues...


  1. Just one comment - I hope you will forgive me this: I am not going to teach you - just recommend some kind of improvement.

    It is a better idea NOT to expand the post too much. Better solution is to split the post into 2, 3 or more parts. This one could have been split into two parts. Of course when you would write the book (or article at PDF format) you could write anything you wish (as long as you need).

    BTW. I have a big respect to your work, knowledge and sharing your experience! :) Well done!

    1. I have just expanded this post -- and another one on blocking -- into two separate posts. Thanks!

  2. Thanks for the suggestion. I try to keep these examples focused, but it is very tempting to expand them to cover relevant ideas. I do get your point!

  3. I think you may consider using some poiting (a, b, c, d, e, I, II, III, IV,...) when explaining all the variations. This way you can relate to the specific line of play without the need to describe it ("You can compare variations "a" with "c" to see the difference at move 4", etc.).

    I know why it is useful as I did the same (or very similiar) job as you are doing now... fifteen years ago. The more material you present - the bigger chance to get lost (without the pointers like I mentioned above). That's my suggestion to make the text much clearer! :). I hope you know what I mean.