Year 378 (CCCLXXVIII) was a common year starting on Monday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Valens and Augustus (or, less frequently, year 1131 Ab urbe condita). The denomination 378 for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
Gothic War: Valens sends Sebastian with a body of picked troops (2,000 men) to Thrace and renews the guerrilla war against the Goths. He chases down small groups of Gothic raiders around Adrianople.
July – Frigeridus, Roman general, fortifies the Succi (Ihtiman) Pass to prevent the "barbarians" from breaking out to the north-west (Pannonia).
Gratian sets out from Lauriacum (Austria) with a body of light armed troops. His force is small enough to travel by boat down the Danube. He halts for four days at Sirmium (Serbia) suffering from fever.
August – Gratian continues down the Danube to the "Camp of Mars" (frontier fortress near modern Niš), where he loses several men in an ambush by a band of Alans.
Fritigern strikes south from Cabyle, following the Tundzha River towards Adrianople, and tries to get behind the supply lines to Constantinople.
Roman reconnaissance detects the Goths. Valens, already west of Adrianople, turns back and establishes a fortified camp outside the city.
The Goths, with their wagons and families vulnerable to attack, withdraw back to the north. Roman scouts fail to detect the Greuthungi cavalry foraging further up the Tundzha valley.
Fritigern sends a Christian priest to the Roman camp with an offer of terms and a letter for Valens. The peace overtures are rejected.
Valens leads an elite Roman army to Thrace to confront revolts, but is defeated in the Battle of Adrianople.[1]
The Goths attack Adrianople; they attempt to scale the city walls with ladders but are repelled by the defenders, who drop lumps of masonry.
The Goths, supported by the Huns, move on to Constantinople. Their progress is checked by the Saracens, recruited from Arab tribes who control the eastern fringes of the empire.
October – The Greuthungi, faced with food shortages, split off and move west into Pannonia. Followed by their families, they raid villages and farmland.
