Editing 421 (section)

== Events ==
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=== By place ===

==== Roman Empire ====
* [[February 8]] &ndash; [[Constantius III]] is appointed co-emperor (''[[Augustus (title)|Augustus]]'') with his ineffectual brother-in-law, [[Honorius (emperor)|Honorius]], and becomes the real ruler of the [[Western Roman Empire]].
* [[March 25]] &ndash; [[Venice]] is founded at twelve o'clock noon (according to legend) with the dedication of the first church, [[San Giacomo di Rialto|San Giacomo]], at the islet of [[Rialto]] ([[Italy]]).  
* [[June 7]] &ndash; Emperor [[Theodosius II]] marries [[Aelia Eudocia]], a woman of Greek origin. The [[wedding]] is celebrated at [[Constantinople]] with [[chariot racing]] in the [[Hippodrome of Constantinople|Hippodrome]].<ref>{{Cite book |last=Holum |first=Kenneth G. |title=Theodosian Empresses: Women and Imperial Dominion in Late Antiquity |date=1989-10-25 |publisher=University of California Press |isbn=978-0-520-06801-8 |pages=115 |language=en}}</ref>
* [[September 2]] &ndash; Constantius III dies suddenly of an illness; his wife [[Galla Placidia]] becomes, for the second time, a [[widow]]. She departs with her children [[Justa Grata Honoria|Grata Honoria]] and [[Valentinian III|Valentinian]] to the court of Constantinople.
* [[Castinus campaign against the Franks]]: A Roman army under command of [[Castinus]] fights against the Franks in Northern Gaul.

==== Europe ====
* [[Rugila]], chieftain of the [[Huns]], attacks the [[Roman diocese|diocese]]s of [[Diocese of Dacia|Dacia]] and [[Diocese of Thrace|Thrace]] ([[Balkans]]). Theodosius II allows [[Pannonia (Roman province)|Pannonian]] [[Ostrogoths]] to settle in Thrace, to defend the [[Danube]] frontier.{{citation needed|date=June 2020}}
* The [[Franks]] conquer new territories in their kingdom and sack the old [[Roman Empire|Roman]] capital ''[[Augusta Treverorum]]'' (modern [[Trier]]).

==== Persia ====
* [[Roman–Sassanid War (421–422)|Roman–Sassanid War]]: Theodosius II starts a war against the [[Sassanids]], sending an expeditionary force under command of [[Ardabur (consul 427)|Ardaburius]], and invades [[Mesopotamia]]. 
* Autumn &ndash; Ardaburius devastates [[Aghdznik|Arzanene]] ([[Kingdom of Armenia (antiquity)|Armenia]]) and forces the Persians to retreat to [[Nusaybin|Nisibis]] ([[Syria]]). King [[Bahram V]] allies himself with the [[Lakhmids|Lakhmid Arabs]] of [[Al-Hirah|Hirah]].
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