Division of Empire follows the lives of Constantine the Great's three sons--Constantine II, Constantius II, and Constans--beginning with the death of their father in 337 AD and tracing how they first shared the empire as a triarchy, until Constantine II was killed by Constans in the civil war of 340, and then Constans was murdered by a usurper in 350. William Lewis uses their story as a case study for how division works, as a process rather than a singular event.