Lucena position

From Wikipedia, the free encyclopedia

The Lucena position, White wins.

The Lucena position is one of the most famous and important positions in chess endgame theory. It is fundamental in the rook and pawn versus rook endgame.

1 Introduction
2 The winning method: building a bridge
- 2.1 Black to move
3 Alternate plan for the defense
4 Conclusion
5 See also
6 References
7 Further reading
8 External links

[edit] Introduction

The so-called Lucena position is named after the Spaniard Luis Ramirez Lucena, although is something of a misnomer, because the position does not in fact appear in his book on chess, Repetición de Amores e Arte de Axedrez (1497). It does appear, however, in Alessandro Salvio's Il Puttino (1634), a romance on the career of the chess player Leonard da Cutri, and it is in that form that it is given here (Müller and Lamprecht, 2001:179).

The position is shown to the right (it should be noted that the position can be moved as a whole or mirrored so that the pawn is on any of the files b through g). White's aim is to either promote his pawn or else compel Black to give up his rook for it — either result will leave White with an overwhelming material advantage and a straightforward win. White has managed to advance his pawn to the seventh rank, but it is prevented from queening because his own king is in the way. White would like to move his king and then promote his pawn, but is prevented from moving to the a-file by the black rook, and prevented from moving to the c-file by the black king.

The essential characteristics of the position are:

the pawn is any pawn except a rook pawn
the pawn has advanced to the seventh rank
the attacking king (the one with the pawn) is on the queening square of its pawn
the attacking rook cuts off the opposing king from the pawn by at least one file
the defending rook is on the file on the other side of the pawn

An obvious approach by White such as

1.Rd1+ Ke7

2.Kc7

gets nowhere (these moves are given in algebraic chess notation). Black can simply harass the white king with checks, and White makes no progress:

2. ... Rc2+

3. Kb6 Rb2+

4. Ka7 Ra2+

5. Kb8 Kd8

brings White back where he started.

[edit] The winning method: building a bridge

In the Lucena position, white has a winning method that works for any pawn except a rook pawn (i.e. on the a- or h-file). (However, the method also works with a rook pawn if the white rook is already on the fourth rank, the black rook isn't on the file adjacent to the pawn, and white is to move.) There is an alternate method for winning this type of position that works only for pawns on the c-file through the f-file, see Rook and pawn versus rook.

In the Lucena position above, White can win with

1. Rd1+ Ke7

2. Rd4!.

Now, if Black plays a "waiting" move, such as

2...Ra1

hoping to harass the white king with checks again as in the above variation, White continues

3. Kc7 Rc1+

4. Kb6 Rb1+

5. Kc6 Rc1+ (or 5. Ka6 Ra1+)

6. Kb5 Rb1+

7. Rb4!.

The black rook can no longer check the white king and Black cannot prevent the pawn from queening. White's shielding his king and pawn with the rook in this way is known as "building a bridge".

It is important that the white rook go initially to the fourth rank if Black uses his most active defense: repeatedly checking the white king. If Black abandons this defense, the white rook can build a bridge on the fifth rank. In the line above, after

5. Kc6

if Black moves

5... Ke6

there is a trap for White: if 6. Rd5?? (to build a bridge on the fifth rank) then 6.... Rxb7! draws. However, if

6. Rd6+ Ke7

7. Rd5

and White can build a bridge on the fifth rank by getting the rook to b5, the king to b6, and then the pawn can promote (Ward 2004:48-49) (position reflected).

[edit] Black to move

If Black is to move in the diagramed position, he can prevent the white rook from going to the fourth rank, but then White still wins:

1... Ra4

2. Rd1+ Ke7

3. Kc7 Rc4+

4. Kb6 Rb4+

5. Ka6 Rb2

(The black rook is not far enough away to keep checking: if 5... Ra4+ then 6. Kb5 wins.) Now White wins by blocking the checks with

6. Rd5

followed by

7. Rb5 (Emms 1999:17) (position reflected).

[edit] Alternate plan for the defense

Alternative approaches are no better for Black. After 1. Rd1+ Ke7 2. Rd4 above, after

2...Rb2

for example, White can still carry out his plan as above, or he can win with the simple

3.Ra4 Kd7

4.Ka8 (or 4.Ka7) Kc7

5. Rc4+

chases the black king away and allows the pawn to promote (or 5. b8=Q Rxb8 6. Rc4+ wins the rook).

[edit] Conclusion

Rook and pawn endgames occur quite often in chess, and this position is very important since endgames may simplify to it. As it is a known win, endgames sometimes revolve around the player with the pawn trying to reach the Lucena position and the other player trying to prevent it.

[edit] See also

[edit] References

John Emms (1999). The Survival Guide to Rook Endings. Everyman Chess. ISBN 1-85744-235-0.

Karsten Müller and Frank Lamprecht (2001). Fundamental Chess Endings. Gambit Publications. ISBN 1-901983-53-6.

Chris Ward (2004). Starting Out: Rook Endgames. Everyman Chess. ISBN 1-85744-374-8.

[edit] Further reading

Reuben Fine and Pal Benko (1941, 2003). Basic Chess Endings. McKay. ISBN 0-8129-3493-8. The Lucena position is diagram 307 in the first edition and diagram 623 in the second edition.