The sudden death of Alexander III in 323 BC triggered a series of crises and upheavals, which eventually led to the empire's break-up. The question of the succession was settled by the proclamation as kings of both Philip III Arrhidaios and the as yet unborn Alexander IV. As they were unable to exercise their function as rulers, this was undertaken by a team of generals.
The most important positions were held by Perdikkas, who was commander of the royal forces in Asia and in effect the main wielder of power, and Antipater, who was in charge of European affairs, guardian of the two kings and regent of Macedonia. Among the regional governors, those who rose to prominence were Lysimachos, governor of strategically vital Thrace, and Ptolemy I, governor of fertile and wealthy Egypt. This arrangement did not last long.
Alexander III had died before having created the necessary infrastructure, which, by levelling the cultural, religious, social and economic differences of the empire's peoples, would maintain its unity. The Successors -- as they were called -- contended for control of the empire with constant clashes in the military and diplomatic fields. Perdikkas first and later Antigonos I Monophthalmos strove to secure sole rule.
Antigonos I Monophthalmos
late 4th century BC
Thus, after nearly five decades of constant clashes, in the course of which both the Argead kings and some of the Successors perished, three states were formed within the empire of Alexander the Great: the Macedonian state (which included Macedonia, Thessaly, and possessions in southern Greece), first under the descendants of Antipater and then of Antigonos; the state of Seleukos in the East, and the state of Ptolemy I in Egypt.