The imperial court of the Achaemenids is beset by factionalism among the lateral family branches by the time Xerxes' successor, Artaxerxes I, dies in 424 BCE, a condition that will persist until the death in 330 BCE of the last of the Achaemenians, Darius III, at the hands of his own subjects.

Alexander the Great of Macedon, envisioning a new world empire based on a fusion of Greek and Iranian culture and ideals, accelerates the disintegration of the Achaemenian Empire.

He is first accepted as leader by the fractious Greeks in 336 BCE and by 334 BCE has advanced to Asia Minor, an Iranian satrapy.

The Middle East: 345–334 BCE

Persian Decline and the Rise of Alexander the Great

The era from 345 to 334 BCE marks the final years of Persian authority under Artaxerxes III Ochus and his successors, a period characterized by internal instability, palace intrigue, and diminishing imperial cohesion. Artaxerxes III attempts to reverse the gradual weakening of Persian dominance through harsh and often violent methods, including punitive campaigns against rebellious provinces such as Phoenicia and Egypt. In 343 BCE, after a fiercely contested military campaign, he successfully reconquers Egypt, reinstating Persian control after decades of independence.

Artaxerxes III's reign abruptly ends in 338 BCE when he is poisoned by his court eunuch and advisor, Bagoas, who subsequently installs Artaxerxes’s son, Arses, on the throne. However, Arses rules briefly, himself falling victim to assassination orchestrated by Bagoas two years later. In 336 BCE, Bagoas places Darius III Codomannus on the Persian throne. Contrary to Bagoas's expectations, Darius swiftly eliminates the manipulative eunuch, securing power for himself but inheriting a fragile and fractious empire.

This internal turmoil coincides with the rapid ascent of Macedonia under Philip II and, following Philip’s assassination, his son Alexander the Great. By 334 BCE, Alexander commences his historic invasion of Persian territory, crossing the Hellespont into Anatolia. The Persian Empire, weakened by internal conflicts and incapable of mounting an effective defense, faces an unprecedented existential threat as Alexander’s campaign signals the imminent end of centuries-long Persian dominance in the Near East.

Bagoas has risen to such power in Persia that he has become the real master of the Achaemenid Empire, Artaxerxes doing nothing without his advice.

In 338, Bagoas murders Artaxerxes—poisoned by his physician at the order of the eunuch—and all the king's sons except the youngest, Arses, whom he places on the throne.

Persia begins to lapse into anarchy.

Bagoas murders Arses, who had attempted to poison him, in the Persian capital, and in 336 elevates to the throne a collateral heir and former satrap of Armenia, the forty-five-year-old son of Arsames, a nephew of Artaxerxes.

The prince takes the throne as Darius III (called Codomannus by the Greeks).

When Darius asserts his independence, Bagoas attempts to poison him, but the king has been warned and forces Bagoas to drink the poison himself.

Darius manages to put down yet another rebellion in Egypt, this one under Khababash in 337-336.

Philip will presently lead the grand army into Asia, and the Greeks will be with him.

Perhaps some Macedonian soldiers, who might have preferred Athenian loot to an Athenian alliance, are puzzled about Philip's motives.

Thus, it may be for the benefit of such doubters that Philip has himself depicted in a domestic Macedonian context (he would surely not risks such a thing in Greece) as a “thirteenth Olympian god.”

On the eve of the Persian invasion, however, during the wedding of his daughter, Cleopatra, to his brother-in-law, Alexander of Molossia in June/July 336, the forty-six-year-old Philip is assassinated in mysterious circumstances, perhaps at the instigation of Persian king Darius III.

The assassin, a bodyguard (somatphylax) named Pausanias, is quickly slain, perhaps accidentally, by one Leonnatus; but suspicion immediately falls upon Alexander, never far from Philip's side that day, and Alexander's abused mother Olympias and her political party, those with most to gain from Philip's death.

Alexander, however, is quickly presented to the army as Macedon's new king, and immediately executes two highly placed suspects, the princes of Lyncestis, alleged to be behind Philip's murder, along with all possible rivals and the whole of the opposition faction.

Not many actual rivals have to be eliminated, however, because Alexander's succession is not in serious doubt.

Amyntas is still alive, but there is no reason for Alexander to see him as a threat (in any case, he is probably dead by 335).

Olympias, on her return from Epirus, has Cleopatra and her infant daughter killed.

Ptolemy returns from exile also and joins the King's bodyguard.

Egypt revolts from Persian rule in 338 BCE following the assassination of Ataxerxes.

His successor, Darius III, invades Egypt in 334 BCE to reconquer the rebellious province.

Alexander III of Macedon, leading some thirty thousand infantry and five thousand cavalry, invades Asia Minor in 334 in fulfillment of his father’s dream of punishing Persia for the Greco-Persian Wars and for its dominance thereafter of the Balkan Peninsula.

As soon as Alexander crosses the Hellespont, he casts his spear into Asian soil and openly declares that he lays claim to all Asia, which is at this time a fluid geographical concept.

In a romantic gesture inspired by Homer, he visits Troy, paying due religious honor to the tombs of the heroes Achilles and Ajax.

He now marches on Phrygia, where Darius III, the Achaemenid king of Persia, waits with an army.

Alexander confronts his first Persian army at the Granicus River (modern Kocabas, flowing into the Sea of Marmara) in May/June 334.

This is not the central army of the Persian king but a very sizable force levied by the satraps from Anatolia itself, numbering perhaps forty thousand and led by three satraps.

Darius has made no serious preparations to resist the Macedonian invasion.

Alexander's shock troops ford the stream and clamber up the bank under a shower of javelins.

Alexander follows and charges the generals, who are concentrated in the left center of the Persian line, leading the right wing with a battle cry to the god of battle.

He kills two relatives of the Persian king, Darius, and is himself saved from death by his cavalry commander, Cleitus the Black.

The Persian plan to tempt Alexander across the river and kill him in the melee almost succeeds; but the Persian line breaks, and Alexander's victory is complete.

Darius' Greek mercenaries are largely massacred, but two thousand survivors are sent back to Macedonia in chains.

According to Alexander's biographer, Arrian (second century CE), the struggle has cost the Macedonians only one hundred and fifteen men.

This victory exposes western Asia Minor to the Macedonians, and most cities hasten to open their gates.

The tyrants are expelled and (in contrast to Macedonian policy in Greece) democracies are installed.

Alexander thus underlines his Panhellenic policy, already symbolized in the sending of three hundred panoplies (sets of armor) taken at the Granicus as an offering dedicated to Athena at Athens by “Alexander son of Philip and the Greeks (except the Spartans) from the barbarians who inhabit Asia.” (This formula, cited by the Greek historian Arrian in his history of Alexander's campaigns, is noteworthy for its omission of any reference to Macedonia.)

However, the cities remain de facto under Alexander, and his appointment of Calas as satrap of Hellespontine Phrygia reflects his claim to succeed the Great King of Persia.

Ephesus submits to Alexander in 334 BCE, but when …