 As the reign of the Diadochi persisted from the late 4th century to the mid-1st century BC, they grew to rely more and more on an increasingly heavier and longer-speared phalanx to ensure victory.Complementary arms of the later Hellenistic armies were neglected, fell into disuse, or became the province of unreliable mercenaries and subject peoples.Sound and creative tactics became increasingly rare, and were replaced by the belief that unbreakable phalanx walls could carry the day.