The 4th century was the time period from AD 301 (represented by the
Roman numerals CCCI) to AD 400 (CD) in accordance with the
Julian calendar. In the West, the early part of the century was shaped by
Constantine the Great, who became the
first Roman emperor to adopt Christianity. Gaining sole reign of the empire, he is also noted for re-establishing a single imperial capital, choosing the site of ancient
Byzantium in 330 (over the current capitals, which had effectively been changed by
Diocletian's reforms to
Milan in the West, and
Nicomedeia in the East) to build the city soon called Nova Roma (New Rome); it was later renamed
Constantinople in his honor.
The last emperor to control both the eastern and western halves of the empire was
Theodosius I. As the century progressed after his death, it became increasingly apparent that the empire had changed in many ways since the time of
Augustus. The two-emperor system originally established by Diocletian in the previous century fell into regular practice, and the east continued to grow in importance as a centre of trade and imperial power, while Rome itself diminished greatly in importance due to its location far from potential trouble spots, like Central Europe and the East. Late in the century Christianity became the official state religion, and the empire's old pagan culture began to disappear.[citation needed] General prosperity was felt throughout this period, but recurring invasions by
Germanic tribes plagued the empire from 376[1][2] CE onward. These early invasions marked the beginning of the end for the
Western Roman Empire.
In
China, the
Jin dynasty, which had united the nation prior in 280, began
rapidly facing trouble by the start of the century due to political infighting, which led to the
insurrections of the northern barbarian tribes (starting the
Sixteen Kingdoms period), which quickly overwhelmed the empire, forcing the Jin court to retreat and entrench itself in the south past the
Yangtze river, starting what is known as the Eastern Jin dynasty around 317. Towards the end of the century, Emperor of the
Former Qin,
Fu Jiān, united the north under his banner, and planned to conquer the Jin dynasty in the south, so as to finally reunite the land, but was decisively defeated at the
Battle of Fei River in 383, causing massive unrest and civil war in his empire, thereby leading to the fall of the Former Qin, and the continued existence of the Eastern Jin dynasty.
According to archaeologists, sufficient archaeological evidence correlates of state-level societies coalesced in the 4th century to show the existence in Korea of the
Three Kingdoms (300/400–668 CE) of
Baekje,
Goguryeo, and
Silla.
Long Fourth Century
Historians of the
Roman Empire refer to the "Long Fourth Century" to the period spanning the fourth century proper but starting earlier with the accession of the Emperor
Diocletian in
284 and ending later with the death of
Honorius in
423 or of
Theodosius II in
450.[3]
365: An
earthquake with a
magnitude of at least eight strikes the Eastern
Mediterranean. The following tsunami causes widespread destruction in Crete, Greece, Libya, Egypt, Cyprus, and Sicily.
376:
Visigoths appear on the
Danube and are allowed entry into the Roman Empire in their flight from the
Huns.