Lucena Position - The Winning Method: Building A Bridge

The Winning Method: Building A Bridge

In the Lucena position, the side with the pawn has a winning method that works for any pawn except a rook pawn (i.e. on the a- or h-file). In some circumstances, it also works for a rook pawn.

In this position, 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 (Ward 2004:48). White's shielding his king and pawn with the rook in this way was described as "building a bridge" by Aron Nimzowitsch (Hooper & Whyld 1992:238).

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):

7... Rc1+

8. Kb6 Rb1+

9. Rb5

and White wins.