380s

Roman Empire

• January or February – Emperor Theodosius I is baptized.
• February 27 – Edict of Thessalonica: Theodosius I, with co-emperors Gratian and Valentinian II, declare their wish that all Roman citizens convert to trinitarian Christianity, in accordance with the patriarchs of Rome and Alexandria, implicitly rejecting the Arianism of the patriarch of Constantinople as heretical.
• Battle of Thessalonica: The Goths under Fritigern defeat a Roman army in Macedonia. Theodosius I retreats to Thessalonica and leaves Gratian in control of the Western Roman Empire.
• Rome's enemies (the Germans, Sarmatians and Huns) are taken into Imperial service; as a consequence, barbarian leaders begin to play an increasingly active role in the Roman Empire.
• November 24 – Theodosius I makes his adventus, or formal entry, into Constantinople.
• Queen Mavia defeats with her Saracen forces the Roman army in southern Syria.

Europe

• The Visigothic chieftain Fritigern dies after ravaging the Balkans; his rival Athanaric becomes king of the entire Gothic nation.

India

• The annexation of western provinces by Chandragupta II gives him control over commerce with Europe and Egypt.

Pacific

• Easter Island, in the south Pacific Ocean, has been occupied by Neolithic seafarers under Hotu Matu'a ("supreme chief"), who about this time begin to fortify the island.

Arts and sciences

• Important works on mathematics and astronomy are written in Sanskrit.

Religion

• Ticonius writes a commentary on the Bible's Book of Revelation.
• A cathedral is built in Trier (Germany).
• The Council of Saragossa is held; Spanish and Aquitanian bishops condemn the teachings of Priscillianism.
• Ambrose introduces popular music into church services.

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