Battle of Ipsus
The Battle of Ipsus was fought in 301 B.C. between the aged Antigonus and Demetrius against Seleucus and Lysimachus as part of the Wars of the Diadochi. Seleucus and Lysiamachus, fighting on behalf of Cassander, won the battle after making excellent use of War Elephants and were aided by deserters from Antigonus' own troops. Antigonus was killed, but Demetrius escaped and set up control over western Asia Minor. Cassander was recognized as king of Macedonia for his triumph, but died the next year.
Encyclopedia of Military History, Dupuy & Dupuy, 1979