Alekhine Defense, Borisenko-Furman Variation

The Borisenko-Furman Variation answers 3...a6 with 4. e4, building a broad pawn center immediately instead of preparing to regain the c4-pawn with e3 or discouraging ...b5 with a4. Black most often uses the free tempo for 4...b5, defending the extra pawn. The alternatives 4...e6 and 4...Nf6, which aim at the center, are less common. The engine rates the position as roughly balanced, and the line is seldom played.