260

By place

Roman Empire

• Battle of Edessa: With a large army, said to number 70,000 men, Valerianus attempts to drive the Persians back from Edessa. The Roman army is surrounded and most of its troops are killed or captured. Valerianus is taken prisoner for the remainder of his life.
• Shapur I sends Valerian to Bishapur and uses the captured Roman army for engineering plans. They construct the Band-e Kaisar.
• Gallienus becomes the sole emperor of Rome; during his reign the Pannonian governor Ingenuus revolts on the Danube.
• Gallienus evacuates the fortifications in the Agri Decumates, covering the Black Forest area in the face of invading Alamanni.
• Gallienus establishes himself at Mediolanum ; he reorganizes the army, supported by elite cavalry, and dispatches troops to the Rhine frontier.
• Postumus, Roman usurper, forms the Gallic Empire and protects the Rhine against an invasion of Germanic tribes.
• Saloninus, son of Gallienus, is proclaimed Augustus by his troops. Postumus besieges Cologne, where Silvanus is praetorian prefect and Roman ruler of Gaul.
• Postumus executes Saloninus and his adviser Silvanus after breaching the walls of Cologne. He is recognized as emperor and establishes his capital at Trier.
• Postumus wins over all the Roman provinces west of the Alps, including Gaul, Britain and Hispania.
• The Roman fort of Wiesbaden is captured by the Alamanni.
• The Franks take control over the Scheldt estuary.

  Persia

• Persian king Shapur I destroys Caesarea Mazaca in Asia Minor.

  China

• The Cao Wei emperor Cao Mao attempts to lead a coup against the increasingly powerful regent Sima Zhao, but is himself killed before it comes to fruition.
• Cao Huan succeeds Cao Mao as emperor of Cao Wei.

  By topic

Arts and sciences

• Earliest known date of chess.

  Religion

• Pope Dionysius convenes a synod at Rome to demand an explanation from bishop Dionysius of Alexandria, who has been charged with separating the members of the Trinity as three distinct deities.
• Paul of Samosata becomes Patriarch of Antioch.