303 BC

By place

Seleucid Empire

• Seleucus I Nicator expands his kingdom throughout Persia as far east as India, but his advance is eventually halted by Chandragupta Maurya, the founder of the Maurya dynasty of India. In a pact concluded by the two leaders, Seleucus agrees to territorial concessions in exchange for 500 war-trained elephants.
• Seleucus refounds the town of Orrhoa in northern Mesopotamia as a military colony and mixes Greek settlers with its eastern population. He names Edessa in memory of the ancient capital of Macedon.

  Greece

• Cassander and Lysimachus persuade Seleucus and Ptolemy to join them in trying to destroy Antigonus.
• Demetrius Poliorcetes occupies Corinth, Sicyon, and Argos in the Peloponnese, and Achaea, Elis and almost all of Arcadia join his side.

  Italy

• The citizens of Tarentum seek the help of the Spartan general, Cleonymus. He is able to pacify the Lucanians with the agreement of the Romans.