Lucena position
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The Lucena position is one of the most famous and important positions in chess endgame theory. It 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. The position is shown to the right (it should be noted that the position can be moved as a whole so that the pawn is on any of the files b-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 such as 1.Rd1+ Ke7 2.Kc7 gets nowhere (these moves are given in algebraic 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 brings White back where he started. White can win, however, with 1.Rd1+ Ke7 2.Rd4. Now, if black plays a "nothing" move, like 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 (or Ka6) Rc1+ 6.Kb5 Rb1+ 7.Rb4. Black cannot prevent the pawn from queening. White shielding his king and pawn with the rook in this way is known as "building a bridge". Alternative approaches are no better for Black. 2...Rb2, for example, stopping White from carrying out his plan, fails to 3.Ra4 followed by 4.Ka8 or 4.Ka7 and queening the pawn. For example, 1.Rd1+ Ke7 2.Rd4 Rb2 3.Ra4 Kd7 4.Ka7 Kc7 5.Rc4+ chases the black king away and allows the pawn to promote. It is important for white's rook to go to the fourth rank. Because the endgame rook and pawn versus rook occurs quite often in chess, this position is very important. As it is a known win, endgames sometimes revolve around one player trying to reach the Lucena position and the other trying to prevent it. Similar positions and the "short side" defense
Not all positions similar to this are wins for the superior side - it depends on the position of the weaker side's rook and king (relative to the opposing pawn), and who is to move. For example, Black to move draws in this diagram. The reason is that Black can check the white king from the side with his rook, and the rook is just far enough away from the white king that if it tries to approach the rook to stop the checks, the rook can get behind the pawn and win it, resulting in a drawn position. For example: 1. ... Ra8+ 2. Kd7 Ra7+ 3. Kd6 Ra6+ 4. Kd5 Ra5+ 5. Kc6 Ra6+ 6. Kb7 Re6, with a draw after winning the pawn, which can no longer be defended by its king. Note that if White's king and pawn are moved to the left, White wins as in the Lucena position above. There must be at least three vacant files between white's king and black's rook for this defense to work. The position of the black king is important too. If Black's king is on g8 instead of g7 in this diagram, White has the move Rf8+ available, which will enable him to win: after 6. ... Re6 as above, 7. Rf8+, followed by 8. e8=Q, with a winning position. So, in positions such as this, the defending king must be on the "short side" (the side of the board that the pawn is on) and the rook at least four files away on the "long side" (the side of the board away from the pawn) for the defense to work. The king needs to be on the short side so it will not block the checks by its own rook. References
See endgame for more references.pl:Pozycja Luceny |