What happened 311 AD

Galerius died in late April or early May 311 from a horribly gruesome disease described by Eusebius and Lactantius, possibly some form of bowel cancer, gangrene, or Fournier gangrene.

On the death of Galerius in May 311, Licinius entered into an agreement with Maximinus Daza to share the eastern provinces between them.

After an illness, Diocletian died on 3 December 311, with some proposing that he took his own life in despair.

The rise of Seleucus in Babylon threatened the eastern extent of Antigonus I territory in Asia. Antigonus, along with his son Demetrius I of Macedon, unsuccessfully led a campaign to annex Babylon. The victory of Seleucus ensured his claim of Babylon and legitimacy. He ruled not only Babylonia, but the entire enormous eastern part of Alexander's empire, as described by Appian: Always lying in wait for the neighboring nations, strong in arms and persuasive in council, he [Seleucus] acquired Mesopotamia, Armenia, 'Seleucid' Cappadocia, Persis, Parthia, Bactria, Arabia, Tapouria, Sogdia, Arachosia, Hyrcania, and other adjacent peoples that had been subdued by Alexander, as far as the river Indus, so that the boundaries of his empire were the most extensive in Asia after that of Alexander. The whole region from Phrygia to the Indus was subject to Seleucus.