Endgame · Rook

The Lucena Position: Building a Bridge

The most important winning position in rook endgames — and the famous trick that cracks it: build a bridge.

The idea

In the Lucena position the attacker has a rook and a pawn one step from queening, the defending king is cut off from the pawn, and the attacking king is boxed in front of its own pawn. The only thing preventing promotion is a stream of rook checks from the side. “Building a bridge” solves it: place your rook on the fourth rank so that, at the decisive moment, it can interpose to block a check — shielding your king and letting the pawn queen.

Step by step

1. 1.Rd1+ nudges the black king a step further away (1…Ke7), then 2.Rd4! is the whole idea — the rook drops to the fourth rank to build the bridge.
2. The White king now walks out toward the checks: 2…Ra1 3.Kc7 Rc1+ 4.Kb6 Rb1+ 5.Kc6 Rc1+ 6.Kb5 Rb1+.
3. Now 7.Rb4! closes the bridge: the rook interposes on the fourth rank, blocking the check (and offering a trade Black cannot accept). Black has run out of safe checks, so after 7…Ra1 8.b8=Q the pawn queens and White is easily winning.

The key rule

Put your rook on the fourth rank first. Then march your king out toward the checking rook; the instant the checks would otherwise be endless, interpose your rook on the fourth rank — the “bridge” — to block the check and trade if needed. The pawn queens.