The Orthodox Variation, Classical System, Benko Attack is a variation of the King's Indian Defense, catalogued as ECO E99. The line runs 1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6 5. Nf3 O-O 6. Be2 e5 7. O-O Nc6 8. d5 Ne7 9. Ne1 Nd7 10. f3 f5 11. g4, reaching the position shown below after 21 half-moves.
Both sides have pawns in the centre (White on d5 and e4, Black on e5), and two pawn captures are available, so the structure is still fluid. Development is level at three minor pieces each. It is Black to move after 11 moves. Both kings have castled kingside, so play tends to shift to the centre and the opposite flank.
On the King's Indian Defense generally: A hypermodern defense where Black allows White to build a big center, then counterattacks it.
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The Orthodox Variation, Classical System, Benko Attack goes 1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6 5. Nf3 O-O 6. Be2 e5 7. O-O Nc6 8. d5 Ne7 9. Ne1 Nd7 10. f3 f5 11. g4. It is a variation of the King's Indian Defense and is catalogued as ECO E99.
The Orthodox Variation, Classical System, Benko Attack is ECO E99. ECO codes group openings by their move order, so nearby codes cover closely related lines of the King's Indian Defense.
Stockfish evaluates the position after 1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6 5. Nf3 O-O 6. Be2 e5 7. O-O Nc6 8. d5 Ne7 9. Ne1 Nd7 10. f3 f5 11. g4 at +0.27 at depth 18, which is a slight pull for White, within normal opening margins. Engine evaluation is only a starting point — at club level the practical value of a line is mostly about whether you know its plans better than your opponent does.
Both sides have pawns in the centre (White on d5 and e4, Black on e5), and two pawn captures are available, so the structure is still fluid. Development is level at three minor pieces each. It is Black to move. Both kings have castled kingside, so play tends to shift to the centre and the opposite flank.