Benko Gambit Accepted

With 4...a6 Black offers a second pawn so that the a- and b-files open quickly, and White's fifth move decides the character of the game. The most common answer, 5. bxa6, is the Fully Accepted Variation. White keeps one extra pawn whether Black recaptures at once with 5...Bxa6 or delays it with 5...g6. Its branches differ mainly in how White handles the f1-bishop and the center: the Yugoslav (6. Nc3 d6 7. e4), the Fianchetto Variation, the King Walk Variation, and the Central Storming Variation, 5...g6 6. Nc3 Bxa6 7. f4.

Other moves return material or refuse the second pawn. In the Modern Variation, 5. e3, White meets 5...axb5 with 6. Bxb5, and Black can then target the loose d5-pawn with ...Qa5 and ...Bb7. The Dlugy Variation, 5. f3 axb5 6. e4, uses the f-pawn to support a quick e4, and 6...Qa5+ 7. Bd2 is a common way to meet it. The Zaitsev System, 5. Nc3 axb5 6. e4, gains space with the knight's support. The Pawn Return Variation, 5. b6 Qxb6, gives the pawn back and keeps the play quiet. The tempting 5. a4 fails, because after 5...axb5 the a4-pawn is pinned against the rook on a1. Black scores slightly better overall, and 5. e3 and 5. b6 do better for White than 5. bxa6. Engines give White a slight edge.