Moscow Variation, Main Line

Blocking with 3...Bd7 is Black's standard answer to the Moscow Variation, also known as the Canal–Sokolsky Attack. Black interposes the queen's bishop and offers to exchange it for White's king's bishop. The trade relieves Black of any problem developing that piece, and Black keeps the flexible pawn pair on c5 and d6. The cost is some simplification and a slightly more passive setup than in the Open Sicilian. White accepts the offer with 4. Bxd7+ in roughly three quarters of games. After 4...Qxd7, the choice is between castling with a later c3 and d4 and a c4 setup that clamps down on d5.

White has two other ways to keep the bishops on the board, 4. a4 and 4. Qe2. Both are much rarer, and 4. Qe2 scores no better than even for White. The engine also rates an immediate 4. c4 highly. Results across the position are close to level, with decisive games far outnumbering draws, and the engine considers it roughly balanced.