Complex sentence: With his emphasis on definitive phrasing through inversion and balance, he prepared the way for the emergence of the heroic couplet, which by the end of the 17th century was the dominant form of English poetry.
Split into simpler sentences: With his emphasis on definitive phrasing through inversion and balance, he prepared the way for the emergence of the heroic couplet. By the end of the 17th century the heroic couplet was the dominant form of English poetry.