Second War of the Diadochi

The Second War of the Diadochi is the conflict between Polyperchon and Cassander, following the death of Cassander's father, Antipater.

Background
The unexpected death of Alexander the Great left his newly created and vast empire without a clear successor. This lack of an arrangement for succession eventually led to war between his top generals, the Diadochi. In a series of shifting alliances they proceeded to carve out kingdoms and independent empires from Alexander's conquests.

Following the first conflict, Antipater became the de facto ruler of Alexander's European territories, while Antigonus gained a similar position in Asia. However, when Antipater died, he left his domain in the hands of his lieutenant, Polyperchon, as opposed to his son Cassander. Cassander, however, had the support of Antigonus, and Ptolemy (the current ruler of Egypt, See Ptolemaic Dynasty), while Polyperchon was supported by Eumenes, Alexander's former secretary, who was then the ruler of Cappadocia.

The War
Cassander gained an early advantage in the war, and was able to force Polyperchon to retreat to Epirus with the infant King Alexander IV. However, from here he joined forces with Alexander's mother Olympias and was able to re-invade Macedon. King Philip Arrhidaeus, Alexander's half-brother, having defected to Cassander's side at the prompting of his wife, Eurydice, was forced to flee, only to be captured in Amphipolis, resulting in the execution of himself and the forced suicide of his wife, both purportedly at the instigation of Olympias.

However, Cassander rallied once more, and was able to take control of Macedon. In doing so, Olympias was killed, and Cassander was able to gain control of the infant King and his mother. In Asia, at the battles of Paraitacene and Gabiene, Eumenes was defeated by Antigonus, allowing Antigonus to control the Asian territories once more.

Aftermath
The war had shifted the balance of power to such a degree that Antigonus could pose a threat to any of the other Diadochi, leading to Cassander, Ptolemy and Lysimachus allying against him in the Third War of the Diadochi. The territories now controlled by Antigonus would later form the basis of the Seleucid Empire.