Complex sentence: In the 10 years from 1144, two successive French counts of Anjou won control of a vast assemblage of lands that would last for 80 years and would retrospectively be referred to as the Angevin Empire.
Split into simpler sentences: In the 10 years from 1144, two successive counts of Anjou won control of a vast assemblage of lands that would last for 80 years. This would retrospectively be referred to as the Angevin Empire.