Based on history, Alexander is tutored by Aristotle, made regent by his father Philip, wins battles in Greece, and then leads the Greeks in the conquest of the Persian empire.
In 356 BC Aeschines debates Demosthenes (Michael Hordern) about war. Demosthenes argues that Athens must fight to defend Olynthus, or Athens will be destroyed. Demosthenes says Philip of Macedonia has been at war against them for a long time.
Philip (Fredric March) in his camp gets a message from Macedonia that his son Alexander was born. Queen Olympias said that a god was born. Philip in his armor returns to Olympias (Danielle Darrieux). Philip was told of the portents and dreams of the Queen. Philip says he had a dream of death. Philip considers whether to kill the soothsayer. Parmenio suggests he could kill his wife and son too. He believes they are most fit to rule Greece, and he advises Philip to go to his wife and son and accept them and show them to the people. Philip does this, holding up the child to the crowd.
Years later young Alexander (Richard Burton) returns with his horse and greets his teacher Aristotle (Barry Jones). Cleitus (Gustavo Rojo) has returned and tells Alexander his father is well and even raided Persian soil. Cleitus has come to train them and new troops. Alexander is eager to fight, and he is tired of studying with Aristotle. Alexander apologizes to Aristotle, who says the Greeks may be united by conquering Persia. Aristotle asks him if he knows how big the Persian empire is and how many peoples live there. Aristotle says he needs patience. Alexander says he chooses glory rather than a long life, like Achilles.
The Greeks train. Aristotle lectures to Alexander and others. Alexander reads aloud from Homer’s Iliad about Achilles. Aristotle advises Philip to give Alexander another year to prepare. Alexander greets Philip who suffers from a wound. Philip says that Macedonians retreat for the first time in twenty years. Philip asks Alexander if he can rule in his palace at Pella, where there is rebellion. Aristotle and Attalus (Stanley Baker) are opposed. Alexander says he can rule. Philip says he will proclaim Alexander regent in Macedonia. Aristotle tells Philip that Alexander is many things and believes himself to be a god.
Alexander and five companions return to Pella and see three men crucified. Alexander enters the palace alone and sees Olympia drinking with others. She comes over to him and says Philip has gone mad. Alexander demands that she send the others away, and they leave. She tells him not to believe Philip’s accusations against her. She says he wants to marry again, someone young. She says when he is regent, they will rule. Alexander goes to see his father Philip, who says he gave Alexander power he must use or lose. Philip tells him he must quell a revolt because his mother wants to rule. Alexander says she is a queen. Philip says there has been no love between her and him for twenty years. Philip says she rules in Alexander’s name. Philip asks him to send his mother away as his first act in Pella. Alexander says it would make him Philip’s pawn. Philip advises him to choose a woman, and Alexander says he chooses her.
At court Philip announces that Alexander is now regent. He leaves Antipater (Friedrich Ledebur) as his advisor. Philip tells him to learn how to be alone. Later while Alexander is lying down, Olympia comes in and speaks to him. He makes her swear that the crown is his, and she says it is by divine right.
Alexander leads his army into battle and burns a city. He says it will be rebuilt and renamed Alexandropolis. He comes home in triumph and embraces Olympia.
Alexander goes to Philip and gives him back the regency ring as ordered. Philip blames him for losing troops while seeking glory. Philip says he has his temper and his ambition. He mentions Alexandropolis and asks him to wait until he dies. Philip says that the niece of Attalus means much to him. Eurydice (Marisa de Leza) introduces herself to Alexander. He walks away, and she asks if he is afraid to speak to her. He laughs, and she says that sits well on him. She suggests there could be a bond between them. He says she is young and beautiful. He asks her why she came there. She wants to know if there will be hate between them. Alexander says his father has had many wives and mistresses. She cries. He says the general Attalus is ambitious. As Philip approaches, she says she wants to love Philip. Alexander asks as what, and Philip says as his queen. Philip asks Alexander that there be no quarrel between them.
Demosthenes speaks to the Athenians that the battle at Charonea will determine who will be master of Greece. The battle begins. Alexander sees Philip fighting and defends him. Alexander is hailed as the hero of Charonea. Athenians ask permission to bury their dead, and Philip denies them. Later Philip drinks in celebration and says he will not destroy Athens because it would be barbaric. He calls out to Demosthenes and shouts, “Philip the barbarian.” Later on his couch Philip tells Eurydice that Alexander saved his life when he could have been king.
The next day Philip announces that his son Alexander will take the ashes of the dead Athenians back to Athens. Philip says he is staying there.
Demosthenes welcomes Alexander to his home, and he meets Aeschines too. Memnon introduces his wife Barsine (Claire Bloom) to Alexander. He tells her that Athens is an idea. He learned from Aristotle that ideas are divine.
Alexander announces that they demand no tribute and that all Athenian prisoners shall go free, but they must promise to fight and provide men and arms and ships. Demosthenes says they have lost the right to choose for what they will die. Alexander says Greece is now united and has a great destiny. Demosthenes says this boy believes what he says. Alexander signs the peace treaty.
Alexander brings gifts to Olympia, who says she is queen no longer. She says Philip has accused her of being unfaithful. She tells Alexander to go to his wedding in peace. Alexander finds Philip drinking after his wedding. Alexander says that Philip calculates everything according to his ambition. Attalus says she is a Macedonian princess. Alexander says his father now sees him as a rival, not a son. Philip says if he did, Alexander would not be alive. Attalus toasts the new queen and asks for a legitimate heir. Alexander accuses him of calling him a bastard. They start to fight, and Philip gets up to stop them but falls down. Alexander points out his father’s failure. Alexander tells his mother to get dressed because they are leaving Pella tonight.
A herald announces that Eurydice’s son has been born, and all exiles may return home. Alexander comes back to the court of Philip and Eurydice. Parmenio says they are marching against Persia with three armies. Alexander asks if his mother will be treated with honor, and Philip agrees. Parmenio says that Harpalus (Jose Marco), Ptolemy (Vergilio Teixeira), his son Philotas (Ruben Rojo), and Pausanias (Peter Wyngard) are to be banished. Alexander asks why, and Philip says they have opposed him. Philotas accepts. Attalus asks Pausanias how he will be able to live without his god Alexander. Philip laughs, and Alexander restrains Pausanias.
Alexander finds Pausanias drinking with Olympias. She asks Alexander what is in Philip’s mind. Philip and Alexander walk in a procession. Philip asks Alexander to walk in front of him. Pausanias comes out and stabs Philip. Pausanias is caught, and Alexander kills him. Eurydice asks the gods to curse the killer, whoever he may be. Alexander before the dead Philip swears it was neither in his hands nor in his heart.
Alexander says that the Macedonian army decides who shall be their king. Alexander makes a speech how he slew his friend who killed his father. He says they have gathered to be led to the greatest victory ever, the conquest of the Persian empire. He says nothing has changed but the name of the king. The soldiers shout, “Alexander.” Alexander sits on the throne, and he speaks to the Greek delegates and claims the titles of his father and asks the cities to pledge their loyalty. He names the cities Corinth, Thebes, Thessaly, Argos, and they nod; but Memnon of Athens declines because he wants free choice. Alexander exiles Memnon with the approval of Athens. He orders two men to be arrested, and they are stoned to death.
At night Eurydice is being buried, and Parmenio tells Alexander that she committed suicide. At dawn Alexander says he will offer victories to Zeus. Before departing with his army Alexander embraces Olympia. She prays to God that he will have eternal glory even though his life may be short.
In 334 BC Alexander with 30,000 men crosses over to Asia and claims it. King Darius (Harry Andrews) arrives on a car pulled by horses. Memnon advises him to retreat so that Alexander will not get a victory. Memnon asks if they doubt his loyalty. The Persian generals want to fight Alexander at Granicus, and Darius agrees. At his tent Memnon tells Barsine he is not sending her to Babylon. She warns him that he is leading Greeks to death. He says he hates tyranny, but she suggests he hates Alexander more. She understands the Greek idea and says the Greeks will win.
Alexander puts on his helmet for battle and leads the charge against the Persians. They fight on horseback with swords. The Persians are defeated and retreat. Memnon asks Alexander for quarter for his men. Alexander says they fight for pay. Memnon is killed.
Alexander is told the legend of the Gordian knot, that whoever can unravel that knot will rule Asia. Alexander looks at it, and cuts it with his sword. The Greeks conquer Asia Minor. Alexander says the Greeks at Miletus are to be sold into slavery. Barsine speaks out. The next day he says she will be treated according to her rank. She asks why he chooses to be alone. Men bring messages to Alexander that were found on the battlefield. They are from Demosthenes to Darius. Parmenio advises him to go back without the Athenian ships as his father would have done. Alexander remembers his father, and he says he is disbanding their fleet and sending it back. They are in Asia to conquer or to die. He frees the Greeks in chains to go back or fight with him.
Alexander, Barsine, and the others watch the ships sail away. She says grace is where he is and embraces him.
Darius has gathered a great army in Babylon, and he demands that Alexander go back to Greece and sends him gifts with insults. Alexander writes back that he should not have informed him of their gold. He says he will have more glory being a boy who killed and defeated a great king.
In their camp under a full moon the Persians cheer their king. Alexander is told they have a million men. Alexander orders them to make camp. They see the moon being eclipsed. The Persians predict doom, but Alexander says the Greek sun eclipsed the Persian moon, a good omen for them. Alexander prays for victory. Darius prays to expand his kingdom. Alexander sends a message to his men that this is the final battle. He says they are outnumbered, and he tells them to hold and wait. They must kill Darius.
The Persians advance on chariots, and the Macedonian phalanx lets them pass through to be surrounded by infantry. Greeks charge on horses. Alexander throws a spear that kills a man, and Darius runs away. Alexander goes to the throne of Darius, and in the royal tent he finds the Queen and her children, including Roxanne (Teresa del Rio).
Darius continues to retreat, and the Greeks pursue him. The Persians tie up Darius on his car. Then he is untied and told to ride a horse. Darius refuses, and they leave him alone. Alexander finds him dead on his car in a stream. Alexander reads the letter Darius left for him. He tells him to take his daughter Roxanne for his wife that their worlds may become one. Men bring the crown to Alexander, who asks the one who killed Darius to come forward. Two Persians ride forward on horses. Alexander says they will be impaled for all to see that only a king may slay a king.
During the celebration Alexander asks his companions what they want. Parmenio toasts Alexander, who will lead them home again. People see that Babylon is burning. Barsine uses a torch to start a fire in the palace. Alexander says no, it is his palace. Alexander asks if she is jealous. She says only his mother is her rival. Alexander says he is the son of God, not his mother.
Aeschines tells Athenians that Alexander is asking to be proclaimed a god. He has conquered the Persian empire and Egypt. Now he has invaded India. Aeschines asks Demosthenes to proclaim Alexander a god.
Alexander sends Parmenio to protect their lines from attack. Alexander arrests Philotas for high treason, and he is tortured and confesses he plotted with his father Parmenio.
Alexander drinks from a golden cup. Cleitus suggests they bet on a battle between his Macedonian and any Persian. Two men fight, and the Persian wins. Alexander wants to spare the Macedonian, but Cleitus disagrees. Alexander says he is drunk. Cleitus says he saved Alexander’s life at Granicus. The both get angry and are restrained by men. Alexander throws a spear into the back of Cleitus, killing him. Alexander embraces his body and cries.
Ptolemy describes the difficult return from India to Babylon. Alexander says the hearts of men must be won. At Susa he marries Roxanne while his soldiers marry Persian women. Alexander offers a prayer, and he hopes that the Greeks and Persians will be all alike. He says there is much to do, but he collapses. While he lies on a couch between Roxanne and Barsine, the soldiers pass by and look at him. He gives instructions for his body to be thrown into the Euphrates so that it may disappear. He says he came from the gods and returns to them. Ptolemy asks to whom he leaves his empire, and he says, “To the strongest.”
This historical drama is the most famous Macedonian conqueror reflects the aggressive and heroic attributes of the Greeks and the intellectual genius of Athenian culture as represented by Aeschines, Demosthenes, and Aristotle. The Greek conquest of the Persian empire can be seen as revenge for the two Persian invasions of Greece a century and a half earlier. Ultimately the influence of a philosopher like Aristotle has done much more good than the temporary military conquest by the warrior Alexander.