During the 2nd and 3rd centuries, Greece was divided into provinces including Achaea, Macedonia, Epirus and Thrace. During the reign of Diocletian in the late 3rd century, Moesia was organized as a diocese, and was ruled by Galerius. Under Constantine (who professed Christianity) Greece was part of the prefectures of Macedonia and Thrace. Theodosius divided the prefecture of Macedonia into the provinces of Creta, Achaea, Thessalia, Epirus Vetus, Epirus Nova, and Macedonia. The Aegean islands formed the province of Insulae in the Diocese of Asia.