304 CE

Pope Marcellinus dies at Rome after an 8-year reign. The papal throne will remain vacant until 308. Caesar Galerius, perhaps accompanied by Emperor Diocletian, wins his fourth and final victory over the Carpi. Many of the surviving Carpi and Bastarnae are resettled in the Roman Empire, where they are split up. The Bastarnae are not attested after this time, and the Carpi are attested only once more in the 310s. Sixteen Kingdoms: The Xiongnu establishes the Han-Zhao state under Liu Yuan, often seen as the start of the Upheaval of the Five Barbarians.

In the 300s, the 4th century.

Geopolitics & Diplomacy

  • Cheng-Han earns its independence from Jin dynasty.source
  • Sixteen Kingdoms: The Xiongnu establishes the Han-Zhao state under Liu Yuan, often seen as the start of the Upheaval of the Five Barbarians.source

Conflict & Security

  • Caesar Constantius I besieges a Germanic raiding force on an island in the Rhine and forces their surrender.source
  • Biryu becomes king of the Korean kingdom of Baekje.source
  • Caesar Galerius, perhaps accompanied by Emperor Diocletian, wins his fourth and final victory over the Carpi. Many of the surviving Carpi and Bastarnae are resettled in the Roman Empire, where they are split up. The Bastarnae are not attested after this time, and the Carpi are attested only once more in the 310s.source

Health & Medicine

  • Diocletian, while inspecting the Danube border, becomes seriously ill.source

Deaths

  • January 21 – Saint Agnes of Rome (martyred by fire) (born c. 291)source
  • March 19/20 – Sima Ai, Chinese prince of the Jin dynasty (executed) (born 277)source
  • May 12 (or 303?) – Saint Pancras of Rome (martyred by beheading) (born c. 289)source
  • October 25 – Pope Marcellinus dies at Rome after an 8-year reign. The papal throne will remain vacant until 308.source
  • December 25 – Saint Anastasia of Sirmium (martyred by beheading)source
  • Saint Alban (martyred by beheading) (possibly 309)source
  • Saint Juliana of Nicomedia (martyred)source
  • Saint Gorgonius of Nicomedia (martyred)source
  • Saints Theodora and Didymus (martyred by beheading)source
  • Saint Vincent of Saragossa (martyred)source
  • Saint Florian (martyred by drowning)source
  • Saint Lucy of Syracuse (martyred by fire and sword)source
  • c. August 10 – Saint Philomena (martyred by beheading)source
  • Saint Margaret the Virgin (martyred by beheading)source