Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6/4. Ba4/4...Nf6/5. O-O/5...Be7/6. Re1/6...b5/7. Bb3/7...d6/8. c3/8...O-O/9. h3/9...Bb7

=Ruy Lopez, Flohr System=

This is the main theoretical battleground in the Ruy Lopez today. Black's bishop aims at the White e-pawn, which will be ganged up on through moves like ...Re8 and ...Bf8, followed by taking on d4 to maximize the pressure. Meanwhile Black maintains maximum flexibility for the queen's knight: it may go to the traditional square a5, or to b4 once the c-pawn captures on d4. Karpov favored this line in his glory days of the '70s and '80s. Now it has greatly decreased in popularity in the last twenty years, but still leads to very complex, difficult positions.

Theory table
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'''1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 b5 7. Bb3 d6 8. c3 O-O 9. h3 Bb7'''