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Could Alexander the Great have conquered the Roman Empire?
Let’s imagine that Alexander the Great, with all his Empire and army, suddenly found himself in the time of the Roman Empire’s peak. That is, in the second century AD, during the reign of Emperor Trajan. Naturally, the fierce Alexander, the invincible commander always thirsting for new conquests, would want to measure his strength against the Romans. What would be the outcome of a clash between the two greatest empires of antiquity?
What are the strengths of the opposing sides? Trajan assembled the largest combined army in Roman history for the war against the Dacians. Since this war was fought in the eastern provinces, and Alexander’s Empire was to the east of the Roman territories, we can assume the Roman forces would be roughly the same in number. That would be 12 legions, 16 alae, and 62 auxiliary cohorts, with a total strength of up to 200,000 men. Theoretically, the Romans could transfer additional forces to counter the new threat, but only at the expense of weakening the other borders of their Empire.
What forces can Alexander muster against the Romans? His army reached its maximum size at the beginning of the Indian campaign, numbering around 120,000 soldiers. Alexander could not have gathered a more significant force, and managing such a large and diverse army (of which only about 30,000 were Macedonians, the rest being from conquered peoples or mercenaries) presented a huge problem.
In India, he faced the army of the King of Magadha. Reports indicated that his opponent had 200,000 infantry, 20,000 cavalry, 2,000 chariots, and 2,000 elephants. Alexander was confident in his victory. Thus, Alexander would undoubtedly decide to engage in battle upon learning that the Roman army numbered 200,000 men.
