Complex sentence: Originally, Classical scholars treated the "Iliad" and the "Odyssey" as written poetry, and Homer as a writer, yet, by the 1920s, Milman Parry (1902--1935) had launched a movement claiming otherwise.
Split into simpler sentences: Originally, Classical scholars treated the "Iliad" and the "Odyssey" as written poetry, and Homer as a writer. Yet, by the 1920s, Milman Parry (1902--1935) had launched a movement claiming otherwise.