380 Manuel Mamikonian’s Revolt▲
Persuaded by the treacherous Meruzhan Artsruni that the Persians were plotting to kill him, the Armenian regent Manuel Mamikonian attacked and massacred the 10,000-strong Persian cavalry detachment in Armenia. Shah Ardashir II (379–383), who had recently succeeded his brother Shapur II, responded by sending a number of armies against Armenia, but was unable to restore his authority over the kingdom. in wikipedia
380 Judaism in Himyar▲
During his reign, Constantius II (337–361) sent an embassy to the Kingdom of Himyar to promote Christianity but was unsuccessful. Instead the kings of Himyar, who had been moving away from their old polytheistic religions in favor of Judaism since the 320s, formally adopted a mix of Judaism and a minimalist Judaism-inspired monotheism in around 380. This marked the public end of polytheism in Himyar and the closure of its great pagan temples. in wikipedia
22 May–9 Jul 381 First Council of Constantinople▲
In May 381 the eastern Roman emperor Theodosius I convened a council of Christian bishops at the Church of Hagia Irene in Constantinople with the intention of obtaining a consensus on Christian affairs. Rejecting the Arian-leaning views that had been promoted in the East since 337 by the emperors Constantius II and Valens, the assembly confirmed the Nicene Creed that had been established by Constantine the Great and expanded its doctrine to produce the Niceno-Constantinopolitan Creed. However, its assertion that the Bishop of Constantinople was second only to that of Rome would later produce controversy. in wikipedia
3 Oct 382 Roman–Gothic Peace▲
After lengthy negotiations, the Romans and Goths formally agreed to peace in October 382. The exact terms of the treaty are uncertain, but they were unusually lenient on the Goths, granting them lands in Lower Moesia, Scythia, and possibly Macedonia in return for providing military support to Rome. Although dispersed by the treaty—and with no recognized leader surviving the war—the Goths retained their autonomy and a level of unity as foederati within the Empire. in wikipedia
Jul 383 Revolt of Magnus Maximus▲
By the early 380s discontent was brewing among the troops of the western Roman army, allegedly over Gratian’s preferential treatment of a force of Alans that he had recently recruited. At the same time Magnus Maximus, commanding officer in Britain and an experienced general, was apparently angered that not only had his relative Theodosius had been appointed eastern emperor instead of him, but that he had decided not to share power with him. Needing little encouragement, the British legions rose up in the summer of 383 and proclaimed Maximus as emperor. in wikipedia
Aug 383 Battle of Paris▲
Upon being declared emperor, Magnus Maximus crossed into northern Gaul, where he was welcomed by the Rhine legions (July 383). Determined to suppress the uprising, Gratian intercepted the usurper near Lutetia (Paris) in August but, after five days of indecisive skirmishing, his Mauri cavalry deserted him, followed by most of the rest of his troops. Left with only three hundred loyal cavalry, Gratian fled for the Alps. in wikipedia
383 Second Tanukhid Revolt▲
Although the Tanukhid Arabs had provided troops to support Valens in the Gothic War of 376–382, the new emperor, Theodosius I, began favoring the Goths with positions within the Roman establishment as soon as the war was over. Feeling betrayed, the Tanukhids revolted in 383, but were quickly crushed by local Roman forces. This brought an effective end to the Tanukhid Kingdom, which was supplanted by the Salihids, Rome’s new primary Arab ally in the Limes Arabicus. in wikipedia
25 Aug 383 Death of Gratian▲
After the Battle of Paris (383), Magnus Maximus dispatched his magister equitum, the ethnic Goth Andragathius, to hunt down the fleeing Gratian. Andragathius caught the 24-year-old emperor at Lugdunum (Lyon) and promptly slew him, cementing Maximus’ rule in Gaul and leaving the 12-year-old Valentinian II as the sole legitimate emperor in the West. in wikipedia
384? Cession of Manuel Mamikonian▲
In c. 384 Manuel Mamikonian, the effective ruler of Armenia, placed the Armenian king Arshak III and his kingdom under Roman protection. However, when Mamikonian died the following year, the Armenian nobility rose into revolt and drove Arshak into Acilisene province, in the far western part of the country. The nobles then called on Sasanian Persia for support, encouraging Shah Shapur III to enter eastern Armenia with his army and appoint Khosrov IV as the new king. in wikipedia
385? Gildo and Magnus Maximus▲
In 385 or 386 Valentinian II appointed the Berber prince Gildo as Comes Africae. Gildo had probably known both Theodosius I and Magnus Maximus from the Roman campaign against his brother Firmus in 372–375, so his appointment may have been a compromise between the emperors. Although it appears that Maximus had some influence in Africa in this period, Gildo would ultimately side with Theodosius when war broke out in 387. in wikipedia