Isolated absence of phalanx

The Battle of Ipsus (Ancient Greek: Ἱψός) was fought between some of the Diadochi (the successors of Alexander the Great) in 301 BC near the town of Ipsus in Phrygia. Antigonus I Monophthalmus, ruler of Phrygia, and his son Demetrius I of Macedon were pitted against the coalition of three other sucessors of Alexander: Cassander, ruler of Macedon; Lysimachus, ruler of Thrace; and Seleucus I Nicator, ruler of Babylonia and Persia. [Source: Wikipedia ]