--- title: Roman Empire under Constantine, 306-337 CE: From Civil War to Christian Rule author: Simeon Netchev source: https://www.worldhistory.org/image/19366/roman-empire-under-constantine-306-337-ce/ format: machine-readable-alternate license: Creative Commons Attribution-NonCommercial-NoDerivs (https://creativecommons.org/licenses/by-nc/4.0) updated: 2026-03-26 --- # Roman Empire under Constantine, 306-337 CE: From Civil War to Christian Rule _Authored by [Simeon Netchev](https://www.worldhistory.org/user/simeonnetchev/)_ ## Image File [![Roman Empire under Constantine, 306-337 CE: From Civil War to Christian Rule](https://www.worldhistory.org/uploads/images/19366.png)](https://www.worldhistory.org/uploads/images/19366.png) ## Image Caption The rise of [Constantine I](https://www.worldhistory.org/Constantine_I/) "the Great" (c. 272–337 CE; reign 306–337 CE) occurred amidst the political instability of the later [Roman Empire](https://www.worldhistory.org/Roman_Empire/), following the collapse of [Diocletian](https://www.worldhistory.org/Diocletian/)’s Tetrarchic system. Proclaimed emperor by his troops at Eboracum (York) in 306 CE after the [death](https://www.worldhistory.org/disambiguation/Death/) of his father, Constantius I Chlorus, [Constantine](https://www.worldhistory.org/disambiguation/Constantine/) engaged in nearly two decades of civil [war](https://www.worldhistory.org/disambiguation/War/) against rival claimants. His victory at the [Battle](https://www.worldhistory.org/disambiguation/battle/) of the Milvian Bridge (October 28, 312 CE) over Maxentius (his Italian rival) was a decisive turning point, famously associated with his initial conversion or public support for [Christianity](https://www.worldhistory.org/christianity/). By defeating Licinius (his Eastern co-emperor) in 324 CE, Constantine became the sole ruler of the [Roman](https://www.worldhistory.org/disambiguation/Roman/) world. As sole emperor (324–337 CE), Constantine implemented reforms that fundamentally redirected the [empire](https://www.worldhistory.org/empire/)'s political and religious trajectory. He refined Diocletian’s administrative framework, and overhauled the military by creating a mobile field army (*comitatenses*). His reign is landmark for the Edict of Milan (313 CE), a joint agreement with Licinius that legalized Christian worship and ended state-sponsored persecution. Additionally, he established [Constantinople](https://www.worldhistory.org/Constantinople/) on the site of [Byzantium](https://www.worldhistory.org/Byzantium/) as the new imperial capital; dedicated in 330 CE, it shifted the empire’s strategic and cultural focus toward the eastern [Mediterranean](https://www.worldhistory.org/disambiguation/mediterranean/). #### Editorial Review This human-authored image has been reviewed by our editorial team before publication to ensure accuracy, reliability and adherence to academic standards in accordance with our [editorial policy](https://www.worldhistory.org/static/editorial-policy/). ## About the Author Simeon is a freelance visual designer and history educator, passionate about the human stories that shape the past. - [Linkedin Profile](https://www.linkedin.com/in/simeon-netchev/) ## External Links - [The Reign of Constantine, a.d. 306–337 (Chapter 4) - The Cambridge Ancient History](https://www.cambridge.org/core/books/abs/cambridge-ancient-history/reign-of-constantine-ad-306337/B346E9BB78105974652BCF2626045530) - [Map of the Roman Empire under Constantine the Great / G. Heck, dirt. ; R. Schmidt sculp](https://www.loc.gov/item/95522157/) ## Cite This Work ### APA Netchev, S. (2026, March 21). Roman Empire under Constantine, 306-337 CE: From Civil War to Christian Rule. *World History Encyclopedia*. ### Chicago Netchev, Simeon. "Roman Empire under Constantine, 306-337 CE: From Civil War to Christian Rule." *World History Encyclopedia*, March 21, 2026. . ### MLA Netchev, Simeon. "Roman Empire under Constantine, 306-337 CE: From Civil War to Christian Rule." *World History Encyclopedia*, 21 Mar 2026, . ## License & Copyright Submitted by [Simeon Netchev](https://www.worldhistory.org/user/simeonnetchev/ "User Page: Simeon Netchev"), published on 21 March 2026. The copyright holder has published this content under the following license: [Creative Commons Attribution-NonCommercial-NoDerivs](https://creativecommons.org/licenses/by-nc/4.0deed.en). This licence only allows others to download this content and share it with others as long as the author is credited, but they can't change the content in any way or use it commercially. When republishing on the web a hyperlink back to the original content source URL must be included. Please note that content linked from this page may have different licensing terms.