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In our last lesson, we saw Philip II of Macedon achieve what no Greek before him ever could: the unification of Greece under a single leader. The Battle of Chaeronea established his hegemony, and the League of Corinth provided the political framework for a grand invasion of the Persian Empire. However, just as he was about to launch this campaign, Philip was assassinated, leaving his vast army and even vaster ambitions to his 20-year-old son, Alexander.
This lesson picks up in the chaotic aftermath of Philip's death in 336 BC. Before Alexander could dream of conquering Asia, he first had to secure his own kingdom. We will explore how he ruthlessly consolidated his power, first within Macedon against rivals for the throne, and then across Greece, where rebellious city-states saw a chance to regain their freedom. By the end of this lesson, you will understand the critical steps Alexander took to secure his home front, which enabled him to finally launch his legendary invasion of the Persian Empire.
A Bloody Inheritance: Securing the Macedonian Throne
Philip's death plunged the Macedonian court into a dangerous power vacuum. Alexander was the heir, but his position was precarious. His mother, Olympias, was not Macedonian, and Philip's newest wife, a Macedonian noble named Cleopatra Eurydice, had recently given birth to a son who could be seen by some as a more "legitimate," pure-blooded heir.
To understand the brutal court politics Alexander had to navigate, the following video provides essential context on the family rivalries and the immediate, bloody aftermath of Philip's assassination.
Alexander the Great takes power (video)
Let's turn to a video from Khan Academy. It details the internal power struggle and the ruthless actions taken by Alexander and his mother, Olympias, to eliminate any potential challengers to the throne.
In this video transcript, read the section that begins with the aftermath of Philip's assassination. It starts around the line 'But once Phillip II gets assassinated, you could imagine that many people are wanting to have a go at the throne...'. Focus on who the rivals were and how they were eliminated. It's a stark look at the reality of securing power in the ancient world.
As you've read, Alexander and Olympias moved with terrifying speed. Potential rivals, including Philip's new wife, her infant children, and her influential uncle Attalus, were systematically executed. This "killing spree" demonstrates a core aspect of Alexander's character: a pragmatic and ruthless determination to remove any obstacle to his power. Only after this bloody internal consolidation could he turn his attention to the unrest brewing abroad.
An Object Lesson: The Destruction of Thebes
News of Philip's death and a false rumor that Alexander himself had been killed during a campaign in the north sent a shockwave of hope through Greece. The city-states, chafing under Macedonian rule, saw their moment. Athens, urged on by the great orator Demosthenes, voiced support for a general uprising, and the powerful city of Thebes—once Philip's ally, then his defeated foe at Chaeronea—rose in open revolt.
The Thebans expelled the Macedonian garrison and called for the liberation of Greece. They, and the rest of Greece, were about to receive an unforgettable lesson in the speed and fury of the new king.
The Destruction of Thebes (335 to 334 B.C.E.)
The channel Historia Civilis provides a superb narrative account of this critical episode. This video will walk you through the entire sequence of events, from the rebellion to its brutal conclusion.
Watch the video from the beginning to 09:02. Pay close attention to Alexander's incredible forced march from Illyria to Thebes, the failed diplomacy, and the subsequent siege and destruction of the city. Notice how the fate of Thebes was designed to send a message.
The destruction of Thebes was an act of calculated terror. By razing one of Greece's oldest and most powerful cities to the ground and selling its 30,000 citizens into slavery, Alexander sent an unambiguous message to all other Greek states: opposition would not be tolerated. It meant utter annihilation.
Athens, which had promised aid to Thebes but strategically dragged its feet, got the message loud and clear. Facing the same army that had just erased Thebes, the Athenians quickly surrendered. In a show of political calculation, Alexander spared Athens. He knew he would need its formidable navy for the Persian campaign and that ruling through fear alone was not enough. He demanded the exile of the most anti-Macedonian politicians but eventually settled for a token punishment, securing Athenian compliance without destroying a vital asset.
Test your understanding!
Alexander treated Thebes and Athens very differently after their respective rebellions. What was the purpose behind destroying Thebes, and what was the strategic reason for sparing Athens?
Show answer
The destruction of Thebes was a calculated act of terror. Its purpose was to serve as a brutal object lesson to the rest of Greece, demonstrating that the price of rebellion against Alexander was total annihilation.
He spared Athens for strategic reasons. Athens possessed the most powerful navy in Greece, an asset Alexander knew would be indispensable for his planned invasion of the Persian Empire, which had a massive fleet. Destroying Athens would have been counterproductive to his larger ambitions. This shows his ability to balance ruthlessness with pragmatism.
Launching the Great Campaign
With Greece now pacified by fear and diplomacy, Alexander could finally pivot to his father's ultimate project: the invasion of Asia. This was not just a military undertaking; it was also a masterclass in political maneuvering and symbolic propaganda.
First, he needed to frame the invasion in a way that the Greeks would support, or at least accept.
How Alexander the Great Conquered the Persian Empire
This article from History.com explains the clever political campaign Alexander launched to justify the invasion.
Read the section titled 'Alexander Used Political Campaigns to Rule Greece'. Focus on how Alexander positioned the invasion as a Panhellenic (all-Greek) war of revenge for Persia's invasions over a century earlier.
By casting himself as the leader of a unified Greece punishing an old enemy, Alexander transformed a Macedonian conquest into a patriotic crusade. With the political stage set, he made his final strategic and personal preparations.
The Destruction of Thebes (335 to 334 B.C.E.)
Let's return to the Historia Civilis video to see the final steps Alexander took before crossing into Asia.
Watch from 09:02 to the end (17:02). This section covers several crucial points: Key Appointments: How he managed his senior commanders, leaving the reliable Antipater in charge of Greece and keeping the powerful but potentially rivalrous Parmenion by his side. Finances: His desperate financial situation and how the entire expedition was a high-stakes gamble. Symbolism: His pilgrimage to the site of Troy to honor his hero, Achilles, a deeply significant act for him and his army.
In the spring of 334 BC, having secured his throne, crushed rebellion, and cloaked his ambition in the guise of heroic revenge, Alexander led his army of 37,000 men across the Hellespont. He was leaving a secure base in Greece and Macedon, but marching into a vast empire with an almost empty treasury. The gamble had begun.
Conclusion
Before Alexander could become "the Great," he first had to prove he could hold his father's kingdom together. He did so with a combination of brutal force, shrewd political calculation, and inspiring leadership that would come to define his reign.
Key Takeaways:
- Ruthless Consolidation: Alexander's first act as king was to violently eliminate all potential rivals within Macedon, securing his claim to the throne with the help of his mother, Olympias.
- Control through Terror and Pragmatism: He reasserted Macedonian dominance over Greece by making a terrifying example of Thebes while strategically sparing Athens for its naval strength.
- A War of Revenge: Alexander masterfully framed the Persian invasion as a Panhellenic crusade, uniting the Greeks (at least nominally) behind his leadership as Hegemon.
- The Great Gamble: He launched his campaign with brilliant strategic appointments but on a financial shoestring, relying on quick victories to fund his army. His pilgrimage to Troy highlighted his deep sense of destiny and his use of powerful symbolism.
Preview of the Next Lesson:
Having crossed into Asia, Alexander's army will not have to wait long for its first major test. In the next lesson, we will analyze his first great battle against the Persian Empire: the Battle of the Granicus. There, we will see Alexander's tactical genius and personal courage on full display as he leads his army against the forces of the Persian satraps.