Britannica
Sources used in this answer
- Alexander the Great - Beginnings of the Persian expedition
- Battle of the Granicus
- ancient Greek civilization - Macedonian supremacy in Greece
- ancient Greek civilization - The conquest of Bactria and the Indus valley
- Alexander the Great - Conquest of the Mediterranean coast and Egypt
- ancient Greek civilization - To the Persian Gates
- Macedonia
Why did Alexander the Great invade the Persian Empire?
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Alexander the Great
Alexander the Great, detail from Alexander and Porus, painting by Charles Le Brun, 17th century; in the Louvre, Paris, France.
Alexander the Great’s invasion of the Persian Empire was driven by a combination of strategic, economic, and ideological motivations:
- Panhellenic Revenge: Alexander framed the offensive as a war of revenge for the historical Persian invasions of Greece in 490 BCE and 480 BCE. This narrative served as a powerful moral appeal to the Greeks, helping to unify them under his leadership.12
- Economic Necessity: Upon his accession, Alexander needed the vast wealth of Persia to maintain the professional army established by his father, Philip II, and to pay off significant debts.3
- Strategic Opportunity: The vulnerability of the Achaemenid Empire had been demonstrated by earlier Greek military successes, such as the campaign of the Ten Thousand. Alexander believed that with his balanced army—particularly his elite cavalry and infantry phalanx—he could defeat any Persian force.3
- Personal Ambition: From the beginning of his reign, Alexander was committed to the expedition, viewing it as an unlimited operation to establish himself as the successor to the Great King of Persia.3