Monday, June 7, 2010

What is zugzwang?

For the answer to this question, see the Kavalek column.

We take turns in chess: first White moves, then Black, then White....  Usually, "having the move" is a big advantage: if both sides are threatening mate, you would like it to be your move!  

Whoever moves first, wins
I hope it's my turn!

This is particularly true in the opening: when we speak of tempo (plural "tempi"), we're often talking about getting  your pieces into battle more quickly than your opponent does.  Having the move can only help!  If you look at the three Marshall Defense traps that Frederick posted earlier this week, you'll see that White gained one or more tempi by forcing Black to recapture the d5 pawn, then retreat the recapturing piece.  If you move four pieces out with your first moves and I've only moved one piece out, then you've gained three tempi on me!  It's a little more complicated than that, but this gives you an idea....

But sometimes (more frequently than most chessplayers realize), having the moving is a burden, not a privilege.

White to play
A complicated position!

I remember trying to explain the king and rook versus king mate to elementary students.  They found this position difficult, so I asked their parents to help.  The parents were confused, too!

First, let's pretend it's Black's move:
  • How many legal moves does Black have?
  • In each case (heh!), can you find White's best reply?
Now let's look at the position with White to move:
  • What is the fastest way for White to win?
And now...let's (temporarily) CHANGE THE RULES OF CHESS so that you don't have to move when it's your turn!  (Instead, either player can just say "pass" and skip a turn.)
  • With White to play, what is the fastest way for White to win this position?
One could ask the very same series of questions about another complicated position:

White to play
Another complicated position!

(Remember that the White pawns generally travel "up" the page (or in this case, the screen) and Black pawns travel "down": the queening square for the d6 pawn is d8.)

No answers for the time being: try to figure this out yourselves!

1 comment:

Frederick said...

With the "pass" rule instituted, the first game would continue 1.Rf6 Pass! 1/2-1/2 (draw agreed since White cannot make progress). Similarly, the second game would continue 1.d7 Pass! 1/2-1/2. Without the pass rule, there is no such thing as zugzwang, causing many standard endgame wins (such as these positions) to become draws.