Friday, January 31, 2014

The Vancura Position

So if you've remembered, I issued the following challenge for everyone yesterday:

White to move, can he win?

The answer to this question is: White cannot win, regardless of whose turn to move. The bad position of his rook coupled with Black's active counterpart will guarantee that Black will save half a point with correct play. And yes, this is one of the many examples illustrating the power of active rooks over passive ones.

In fact, this rook endgame position is known as the Vancura Position. It is a draw for Black thanks to the following:

  1. Black's rook attacks the h6 pawn, thus tying White's rook down to its defense.
  2. White's king has no shelter from Black's barrage of rook checks. If the pawn were on g6 instead of h6, then it would be a different story altogether because White can hide his king on h6.
  3. If White tries to push the h-pawn, then Black's rook will just leap to the h-file and continue to tie down White's rook. Then White cannot make any progress as long as Black keeps his rook on the h-file.


If it were Black to move he could just play 1... Rd6, shuffling along the 6th rank and keeping an eye on the h6 pawn. So let's give White the move here:

1. Kg5

Threatening to release the rook from its guard duty with 2. Rb8. Other variations such as 1. Rh7+ Kb6 give White no progress, while 1. h7 Rh6 2. Kg5 Rh1 leads to the draw which we discussed in Point 3.

1... Rc5+

The first of many checks to be unleashed upon the White king

2. Kf6 Rc6+
3. Ke5 

Since 3. Kg7 Rc7+ doesn't achieve anything, White tries to walk closer to Black's rook in order to pick it off...

3... Rg6

... but Black's rook can simply leap along the 6th rank and get out of harm's way

4. Kd5 Rf6 (D)

You can't catch me!

Notice that when Black is not checking White's king, he makes sure that his rook stays on the 6th rank, thus tying down White's rook to defending the h6 pawn. If he feels that shuffling the rook is too boring, he could throw in some variety with 4... Ka7 which would not make much of a difference.

However, Black must be careful not to throw away the game with 4... Rc6?? 5. Rb8+! Kxb8 6. Kxc6 with immediate defeat.

5. Rh7+

Since moving the king or pawn makes no progress, how about checking the king?

5... Kb6

Still no chance! White's rook is still forced to look after the h6 pawn.

6. Ke5 Rc6
7. Kf5 Rc5+
8. Kg6 Rc6+
9. Kg7 Rc7+
10. Kh8 Rc8+ (D)
1/2-1/2

Time to shake hands

White's king cannot escape from the volley of checks, and the pawn can never hope to advance.

The Vancura Position will prove to be a useful building block as we move up the ladder in our investigation of rook endgames.

Sources:
"Silman's Complete Endgame Course" by Jeremy Silman

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