The Marshall Attack is reached after 4. Ba4 Nf6 5. 0-0 Be7 6. Re1 b5 7. Bb3 0-0 8. c3 d5. It features many forcing moves that require players to know theory in order to successfully navigate the opening, and because of this, many White players choose to play "anti-Marshall" systems that avoid these lines. There are also some lines in which White may force early draws.
It should be clear now just how complex the Ruy Lopez can be - and we've only scratched the surface of the lines available in this rich opening system.
