Definition of "tetrarchy"

Constantius was not born to the purple and Maximianus was the only original member of the First Tetrarchy from whom Constantine could satisfactorily derive his rule.

1996, Sam Lieu, “2: Constantine's "Pagan" Vision: The anonymous panegyric on Constantine (310), Pan. Lat. VII(6)”, in Samuel N. C. Lieu, Dominic Montserrat, editors, From Constantine to Julian: Pagan and Byzantine Views: A Source History, published 2003, page 66

The abdication of Diocletian and Maximian in 305, whether long-planned or just the product of the senior emperor's recent ill health, created a second Tetrarchy, in which the dominant figure should have been Galerius.

2010, Roger Collins, Early Medieval Europe, 300-1000, 3rd edition, page 16

His imperial reorganization saw authority divided between four rulers, the Tetrarchy, to oversee the recovery.

2015, David M. Gwynn, chapter I, in Christianity in the Later Roman Empire: A Sourcebook‎, page 15

According to Josephus, Herod Agrippa, who succeeded Antipas in his Tetrarchy, died in the seventh year of his reign; […] .

1830, Edward Greswell, chapter I, in Dissertations Upon the Principles and Arrangement of a Harmony of the Gospels‎, volume 1, page 228

This district was included with Galilee in the tetrarchy of Herod Antipas.

1863, James Hewitt, chapter I, in Scripture Geography‎, page 66

After an adventurous career, Aristobulus' son Agrippa was appointed by Gaius, in 38 C.E., king of the former tetrarchies of Philip and Lysanias and was granted the praetorian ornamenta. Soon after, he was awarded the tetrarchy of his uncle and brother-in-law Herod Antipas […] .

1990, Seth Schwartz, chapter I, in Josephus and Judaean Politics‎, page 110