300 – 310s

Events in the 300s 4

• 300 BC – 300 Yayoi period Rice farming, bronze and iron arrive from the mainland The Yayoi period brought wet-rice cultivation, bronze and iron metallurgy, and the potter's wheel to Japan from Korea and China. These innovations drove population growth and the emergence of stratified society and local chieftaincies — the foundations of the Japanese state.
• 284 – 305 Diocletian — the great reorganiser Diocletian ends the crisis of the third century by systematically reorganising the empire. He creates the Tetrarchy — four co-emperors (two Augusti and two Caesars) ruling different regions simultaneously. He doubles the size of the army, triples the bureaucracy, reforms taxation and the currency, and fixes prices in the Edict on Maximum Prices (301 AD) — the most ambitious price control in history. He conducts the Great Persecution of Christians (303–311 AD) — the last and worst. He retires voluntarily in 305 AD — the only emperor to do so.
• 300 – 538 Kofun period Giant keyhole tombs and the rise of Yamato The Kofun period is named for the massive keyhole-shaped burial mounds (kofun) built for powerful rulers. During this era the Yamato court in the Nara plain rose to dominance over rival polities, laying the basis for a unified Japanese state under the imperial line.
• 306 – 337 Constantine the Great Constantine I reunites the empire after defeating his rivals — culminating in the defeat of Maxentius at the Milvian Bridge (312 AD), where Constantine reportedly sees a cross in the sky with the words "In this sign, conquer." Whether genuine vision or political calculation, Constantine legalises Christianity with the Edict of Milan (313 AD), convenes the Council of Nicaea (325 AD) and founds Constantinople (330 AD) as the empire's new capital on the Bosphorus. His conversion transforms Western history.