Philidor defence

Philidor's defence, usually called "the Philidor", is one of the basic chess openings. It was used often by the 18th century master François-André Danican Philidor, and he published analysis about it in his textbook "L'Analyse du jeu des échecs" (1849).
Variations.
Transposition.
Black can reach a line called the Hanham variation by transposing from the Pirc defence: