The Modern Defense 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 themself. The opening has been most notably used by British grandmastersNigel Davies and Colin McNab. The Modern Defense 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. There are numerous transpositionalpossibilities between the two openings. The Encyclopaedia of Chess Openings classifies the Modern Defense as code B06, while codes B07 to B09 are assigned to the Pirc. The tenth edition of Modern Chess Openings grouped the Pirc and Robatsch together as the "Pirc-Robatsch Defense".
2.d4
Main line: 2.d4 Bg7
White's strongest response to the Modern Defense is 2.d4, to which Black typically responds 2...Bg7. The main continuations are:
suggested the move 3.h4!? as an unorthodox try against 1...g6 2.d4 Bg7, in his annotation to a game against Pal Benko. The idea is to pry open Black's by h4-h5 followed by hxg6, as...gxh5 would greatly weaken the cover to Black's king.
Averbakh System
The Modern Defense, Averbakh System can be reached by the lines:
1.e4 g6 2.d4 Bg7 3.c4 d6 4.Nc3
1.d4 g6 2.c4 Bg7 3.Nc3 d6 4.e4
Possible moves for Black at this point include 4...Nf6, 4...Nc6, 4...e5, and 4...Nd7. The move 4...Nf6 leads to a position of the King's Indian Defence, where White has options 5.Nf3, 5.f3, 5.Be2, 5.f4, and so on.
Unusual White responses
The flexibility and toughness of the Modern Defense has provoked some very aggressive responses by White, including the crudely named Monkey's Bum, a typical sequence being 1.e4 g6 2.Bc4 Bg7 3.Qf3. Other unusual openings can be reached after 1.e4 g6. The Hippopotamus Defence is one such system. Another is the Norwegian Defence which begins 1.e4 g6 2.d4 Nf6 3.e5 Nh5. Transpositions are possible after 2.c4, for example a Maróczy Bind results after 2...c5 3.Nf3 Bg7 4.d4 cxd4 5.Nxd4 and the Averbakh system is reached after 2...Bg7 3.d4 d6 4.Nc3. After 2.Nf3, Black can play 2...c5, transposing to the Sicilian Defense, or 2...Bg7. Following 2.Nc3, Black can transpose to a closed Sicilian with 2...c5 or play 2...Bg7.
