The Roman Emperor Diocletian (ruled AD 284 to 305) reformed the government in the late Roman Empire and established the Tetrarchy. This new system for the first time divided rule of the empire into the Western and Eastern courts, each headed by a person with the title of Augustus. Each of the two Augusti also had an appointed successor, a Caesar, who administered about half the district belonging to his own Augustus (and was subordinate to him). In Diocletian's division, Dalmatia fell under the rule of the Eastern Court, headed by Diocletian, but was administered by his Caesar and appointed successor Galerius, who had his seat in the city of Sirmium. In AD 395, the Emperor Theodosius I permanently divided Imperial rule by granting his two sons the position of Augusti separately in the West and the East. This time, however, Spalatum and Dalmatia fell under the Western Court of Honorius, not the Eastern Court.