Alexander is usually introduced as a prodigy who came from nowhere. He did not. He inherited the best army in the world from his father, and the first thing to understand about him is that machine.
Macedon sat north of the Greek city states, and the Greeks had spent centuries regarding it as a rough place on the edge of things. Philip the Second changed that in twenty years. He reorganised the infantry around a pike about five and a half metres long, held in both hands, so that a formation presented five ranks of points to anyone approaching it. He paid and drilled his men year round, which no city state militia could match. He built a cavalry arm capable of charging home, and he used the two together, the pikes fixing an enemy line in place while the horse went round it.
He also bribed, married and negotiated relentlessly, and when the southern cities finally combined against him he beat them at Chaeronea in 338. Two years later he was murdered at a wedding, by one of his own bodyguards, for reasons that were being disputed within months and have never been settled.
His son was twenty. He killed or exiled his rivals, put down a revolt in the south by destroying the city of Thebes, and then did the thing his father had been preparing when he died. He crossed into Asia.
The Persian Empire was the largest political structure the world had yet produced, running from the Aegean to the Indus, and it was not in decline. It was rich, administratively sophisticated, and could raise armies far larger than anything Macedon could field.
Alexander beat it in three battles over four years. At the Granicus in 334 he broke a Persian force guarding the river crossing into Asia Minor. At Issus in 333 he caught the king himself, Darius the Third, in a coastal bottleneck where numbers could not be brought to bear, and Darius fled the field. At Gaugamela in 331, on open ground of Darius' own choosing, Alexander pulled the Persian line apart by drawing its left wing outwards and driving a wedge into the gap, and Darius fled again.
The pattern is consistent enough to be worth naming. Alexander looked for the point where the enemy line would have to stretch, made it stretch, and went through the tear at the head of his own cavalry. It worked because his infantry could hold a much larger force in place while he did it, and because he was willing to put himself where he could be killed. He was wounded repeatedly.
Between Issus and Gaugamela he did something less glamorous and more revealing. He spent seven months taking the island fortress of Tyre, building a causeway out to it, because leaving a Persian naval base behind him would have let the Persian fleet cut his communications. Then he went to Egypt, which surrendered without a fight, and founded a city at the mouth of the Nile that still carries his name.
Here is the part that is usually skipped. Having destroyed the Persian state, Alexander largely kept the Persian machinery of government.
The empire was administered through provinces under governors called satraps, with a tax system and a road network and a bureaucracy that worked. Alexander did not dismantle it. He replaced some satraps and confirmed others, including Persians. He took over the treasuries, which contained a quantity of stored bullion so large that releasing it into circulation is thought to have moved prices across the eastern Mediterranean.
He also began adopting Persian court practice, wore some elements of Persian dress, and at one point tried to introduce the ceremonial prostration that Persians performed before their king. His Macedonian officers, for whom a king was a first among nobles who could be argued with, found this intolerable, and he dropped it. The tension between conquering an empire and having to rule it as its previous rulers had is visible throughout his last years, and it is the most interesting thing about him.
In 330 the palace complex at Persepolis burned. Our sources disagree about whether this was policy or a drunken accident at a party, and both versions were circulating within a generation.
He kept going. Into what is now Afghanistan and Central Asia, where the campaign turned into three years of grinding counter insurgency against local commanders who would not meet him in open battle. Then over the mountains into the Punjab, where in 326 he fought his last great battle against a regional king named Porus, whose army included war elephants, and won it at some cost.
Then his army refused to go any further. At a river the Greeks called the Hyphasis, the men would not cross. They had been marching and fighting for eight years, they were thousands of miles from home, and the reports said the plains ahead went on for weeks and had more elephants in them. Alexander sulked in his tent for two days, which is exactly what he had been taught the hero of the Iliad did, and then turned back.
The return was worse than the advance. He took part of the army through the Gedrosian desert, and a great many died of thirst. Ancient writers say he chose the route out of pride, because someone had told him no army had crossed it. That may be moralising after the fact, but the losses were real.
In June of 323, in Babylon, after a long drinking party, he developed a fever and died about ten days later. He was thirty two. The causes proposed then and since include typhoid, malaria, alcohol poisoning and murder, and the honest answer is that a fever in Babylon in June needs no exotic explanation and cannot be diagnosed at this distance.
Armies of this size are not free to go wherever the map suggests, and the constraint is food.
A force of forty thousand men, with the cavalry horses, the baggage animals and the civilians who followed it, needed something like a hundred tonnes of grain and a comparable weight of fodder every day, plus water, which is heavier than both. No pre industrial army could carry more than a few days of that. It therefore had to either stay within reach of ships, or move through country that had food in it, at the season when the food was there.
Read the campaign with that in mind and the odd decisions stop being odd. The long detour down the coast to Egypt, the seven month siege of Tyre, the timing of the marches, the splitting of the army into columns in dry country: these follow from the arithmetic. So does the disaster in the Gedrosian desert, which was an attempt to cross ground that could not support the force crossing it.
The other half of the arithmetic is that the food came from somewhere. An army that requisitions a hundred tonnes of grain a day is taking it from farmers who were going to eat it. Cities that surrendered promptly paid in supplies and were left standing. Cities that did not were made into examples: Thebes in Greece was destroyed and its population sold, Tyre and Gaza were stormed with mass executions and enslavements after long sieges that had cost Macedonian lives.
The worst of it was in Central Asia, in the three years of fighting in what is now Afghanistan, Uzbekistan and Tajikistan. There was no single enemy army to defeat, so the campaign became a matter of storming hill forts, burning settlements and killing populations to deny the insurgents support. The ancient accounts, which are broadly admiring of Alexander, describe this without embarrassment because their authors did not think it needed defending.
None of this makes him unusual for a conqueror of his era. It does mean that a chapter which describes only the battles and the founding of cities has described about a third of what happened.
He had not named an heir. Asked on his deathbed who should have the empire, he is said to have answered, to the strongest. Whether he said it or not, it is what happened.
His generals fought each other for forty years. What settled out of that was three large kingdoms and several smaller ones: a Macedonian dynasty ruling Egypt from Alexandria, another ruling most of the old Persian heartland from Syria and Mesopotamia, and a third holding Macedon and its grip on Greece. These are the Hellenistic kingdoms, and they lasted for roughly three hundred years until Rome absorbed them one by one.
That period matters more for European history than the conquest itself. Greek became the working language of government, trade and learning across an enormous zone, in a simplified common form. Cities founded or refounded on Greek lines were planted from the Nile to Central Asia. Alexandria acquired a library and a research institution that produced the best mathematics, astronomy and textual scholarship of the ancient world.
Two long consequences follow from that. When Rome conquered the eastern Mediterranean it did not impose its culture there; it absorbed a Greek one, and educated Romans learned Greek. And when a new religion began spreading out of Roman Judaea three centuries later, it spread along those roads, in that common Greek, and its founding documents were written in it.
This is the chapter in this book where the gap between confidence and evidence is widest, and it is worth being blunt about it.
Firm: the route, the dates, the battles and the outcomes. Cities were founded, coins were struck, an empire changed hands, and the Hellenistic kingdoms are documented in detail.
Very soft: everything about the man. Not one contemporary account survives. Our fullest narrative was written by Arrian around four hundred and fifty years later. Plutarch, Diodorus and Curtius are also centuries removed. All of them were working from earlier books now lost, including memoirs by one of Alexander's own generals and an official campaign historian who was executed for refusing to prostrate himself. So the tradition runs through people with a case to make, and then through Roman era writers with cases of their own.
This is why the anecdotes are unusable as evidence. The cutting of the Gordian knot, the taming of the horse, the tears at having no more worlds to conquer, and most of the reported speeches all come from that late layer.
Contested: whether he had any policy at all beyond conquest. Nineteenth and early twentieth century historians credited him with a vision of uniting mankind. That reading has been largely abandoned, because it rests on late sources and on the assumptions of the historians who liked it. What the evidence supports is narrower: a superb commander who took an empire, kept most of its administration, and died before anyone found out what he intended to do with it.