Tarrasch rule

The Tarrasch rule says that rooks are usually best placed behind passed pawns. A passed pawn has no enemy pawn ahead of it on the same or an adjacent file that can block it or capture it as it advances. The guideline applies to both your own passed pawn and the opponent's.

Behind a friendly pawn, the rook supports it and gains range as the pawn advances. Behind an enemy pawn, the rook attacks it and keeps more room while the pawn approaches promotion. A rook in front of its own pawn, by contrast, often loses mobility because the advancing pawn pushes it toward the edge.

A guideline, not a law

Activity can matter more than ideal placement. If the rook already prevents the enemy king from crossing a rank or file, lateral checks are required, or the rook can collect other pawns, leaving the rear may be correct. Rook pawns also create exceptions: the Vancura position defends from the side, and some positions require a frontal defense.

Use the rule as a first question: can the rook get behind the pawn without losing time or allowing a tactic? Then calculate the concrete position. Models such as Lucena and Philidor show that king placement and checking distance can outweigh a general formula.