The Modern Defence (also known as the Robatsch Defence after Karl Robatsch) is a hypermodern chess opening in which Black allows White to occupy the center with pawns on d4 and e4, then proceeds to Attack and undermine this "ideal" center without attempting to occupy it themselves. The opening has been most notably used by British grandmasters Nigel Davies and Colin McNab.
The Modern Defence is closely related to the Pirc Defence, the primary difference being that in the Modern, Black delays developing his knight to f6. (The delay of ...Nf6 Attacking White's pawn on e4 gives White the option of blunting the g7-bishop with c2–c3.) Transpositional possibilities between the two openings are rife.
The Encyclopaedia of Chess Openings (ECO) classifies the Modern Defence as code B06, while codes B07 to B09 are assigned to the Pirc. The tenth edition of Modern Chess Openings (1965) grouped the Pirc and Robatsch together as the "Pirc–Robatsch Defence".
Robatsch (Modern) Defence, including Monkey's Bum