Lucena position

The Lucena position is one of the most famous and important positions in chess endgame theory, where one side has a rook and a pawn and the defender has a rook. It is fundamental in the rook and pawn versus rook endgame. If the side with the pawn can reach this type of position, they can forcibly win the game. Most rook and pawn versus rook endgames reach either the Lucena position or the Philidor position if played accurately . The side with the pawn will try to reach the Lucena position to win; the other side will try to reach the Philidor position to draw.
The position is named after the Spaniard Luis Ramirez de Lucena, although he did not analyze it or publish it .
Introduction.
The Lucena position is named after the Spaniard Luis Ramírez de Lucena, although it 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 Leonardo da Cutri, and it is in that form that it is given here . Salvio attributes it to Scipione Genovino . It is likely that the error arose from the sixth edition of the "Handbuch des Schachspiels", in which editor Constantin Schwede incorrectly attributed the position to "Lucena 96", possibly as a result of confusion over the references in Antonius van der Linde's 1874 work "Das Schachspiel des XVI. Jahrhunderts".
The position is shown above and below (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:
An obvious approach by White (in the position above) such as 
gets nowhere. Black can simply harass the white king with checks, and White makes no progress: 
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 the Lucena position, White can win with 
Now, if Black plays a waiting move, such as 
hoping to harass the white king with checks again as in the above variation, White continues 
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 was described as "building a bridge" by Aron Nimzowitsch .
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 
if Black moves 
there is a trap for White: if 6.Rd5?? (to build a bridge on the fifth rank) then 6...Rxb7! draws. However, if 
(6.Re4+ followed by either 7.Re8 or (if 7...Kf7) 8.Re5 works as well.) 
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 (position reflected):
and White wins.
If the defending rook is on the rank that would prevent moving the rook to the crucial rank (i.e. 2.Rd4), see Rook and pawn versus rook endgame#Defending rook prevents the bridge.
Black to move.
If Black is to move in the diagrammed position, he can prevent the white rook from going to the fourth rank, but then White still wins:
(The black rook is not sufficiently far away to keep checking: if 5...Ra4+ then 6.Kb5 wins.) Now White wins by blocking the checks with
followed by
Bridge on the fifth rank.
A bridge can also be built on the fifth rank (but it is better to build one on the fourth rank). The main line goes:
Threatening to promote the pawn, Black can just delay it with checks.
and the pawn will promote. Or
Better is 2.Rf8 Kg7 3.Rf4!, back to a bridge on the fourth rank.
and White has a winning (but difficult) queen versus rook endgame (see pawnless chess endgame) .
Alternate plan for the defense.
Alternative approaches are no better for Black. After 1.Rd1+ Ke7 2.Rd4 above, after
for example, White can still carry out his plan as above, or he can win with the simple 
which chases the black king away and allows the pawn to promote. (Or, 5.b8=Q+ Rxb8 6.Rc4+ wins the rook.)
Rook pawn.
The Lucena method also works with a rook pawn if the white rook is already on the fourth rank, the black rook is not on the file adjacent to the pawn, and White is to move. Otherwise, the defending king must be cut off four files from the pawn, as in the diagram. This is not a true Lucena position since the king is cut off by more than one file. White wins:
and White has a won queen versus rook endgame – one that is easier to win than one where the rook is close to its king .
Some exceptions.
Not all similar positions are wins. In this position, Black draws because he can safely check from the side. For this defense to work, there must be at least three files between the defending rook and the attacking king, and the defending king must be positioned such that it does not block the checks; that is, the defending king is on the "short side" of the pawn (the one with fewer files between the pawn and the edge of the board) . (See the "short-side defense" at rook and pawn versus rook endgame for more details.)
Examples from praxis.
In this 2000 game between Rice and Ian Snape, Black uses the above procedure:
Here White deviates from the above:
White resigns, but the alternative is:
and Black wins .
In this position from a 1999 game between Ulf Andersson and Ralf Åkesson, White exchanges pawns in order to get to the Lucena position.
and Black resigned. White will reach a Lucena position: 81...Rg1+ 82.Kf7 Rf1 83.f6 Rf2 84.Kg7 Rg2+ 85.Kf8 Rf2 86.f7 Rg2 (a Lucena position) 87.Rd4+ Kc7 (if 87...Ke6 then 88.Ke8 wins) 88.Ke7 Re2+ 89. Kf6 Rf2+ 90.Ke6 Re2+ 91.Kf5 Rf2+ 92.Rf4 and White wins .
Conclusion.
Rook and pawn endgames occur quite often in chess, about eight to ten percent of all games , . 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.
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 endgame).