Chess Opening Theory/1. e4/1...e6/2. d4/2...d5/3. Nc3/3...Bb4/4. e5/4...c5/5. a3/5...Bxc3/6. bxc3/6...Ne7/7. Qg4/7...O-O/8. Nf3/8...Nbc6/9. Bd3/9...f5

=French Defence, Winawer Variation= Black's last move 9... f5 stopped White's threat of sacrificing the bishop on h7. If White doesn't capture Black's f5 pawn en passant now, then their king bishop's diagonal (b1-h7) will be blocked permanently. Because having their king bishop on a blocked diagonal certainly won't help White's kingside attack at all, White usually decides to capture the f5 pawn en passant 10. exf6. However, in a few games White also played 10. Qh3 - in hope for opening a file on the kingside for their rooks at a later time.

Theory table
'''1. e4 e6 2. d4 d5 3. Nc3 Bb4 4. e5 c5 5. a3 Bxc3+ 6. bxc3 Ne7 7. Qg4 O-O 8. Nf3 Nbc6 9. Bd3 f5'''