The following is borrowed from The Origins of War by Arther Ferrill © 1985 Thames and Hudson Ltd, London.

Alexander at Waterloo
his battle, so decisive in European history, has been refought many times by armchair generals, and we must do it once again, using it as a standard by which to judge Alexander's generalship and his contribution to the art of war. How might Alexander have fought this battle had he been in Napoleon's shoes? First we should remember that scale of the battle, in troop strength and geographically, would not have daunted Alexander. He
had fought opponents more numerous than Wellington's army along lines of about the same length. Gunpowder would have been new to him, but he had some experience in using catapults as field artillerey, at somewhat less range and destructive power. In fact neither French nor British artillery proved decisive at Waterloo. The battle was determined when cavalry and infantry, singly or in combination, closed with the enemy. The big guns at Waterloo could not prevent that from happening.

All military historians agree that Napoleon and Ney made several critical mistakes on the day of Waterloo,
and we can safely assume, based on what we know af Alexander's career, that he would not have made any of them. It is of course theoretically possible that he might have had a bad day too, just as Napoleon did, but unlike Napoleon, Alexander never actually had such a day in his own experience. In any event, the point is not to prove that Alexander was a better general than Napoleon -- merely that Alexander had brought the art of war to a nearly modern level some 2,000 years before the French emperor.

We know that Alexander understood the proper use of an integrated army, a concept he and hes father had
borrowed from the ancient Near East and had improved through the development of good heavy infantry, the Macedonian phalanx.

Napoleon's first mistake was in delaying the initial attack against Wellington for so long, a mistake
compounded by the fact that Prussians were coming to relieve the British. Everything we know about Alexander suggests that he would not have been so sluggish and indecisive. At the Granicus and at Issus Alexander moved from line of column into line of battle and attacked his enemy without delay. In his other battles he always moved vigorously, once he was in tactictal range, to close with the enemy. Furthermore Alexander would not have mounted an attack either with cavalry or with infantry unsupported by the other arm. Ney's use of cavalry unsupported by infantry remains to this day almost inexplicable. Finally, Alexander would not have stayed behind his line the way Napoleon did. Wellington and Ney exposed themselves to risks all day long. Ney went through five horses on the afternoon of the battle, but Napoleon was so far behind his line that he could not intervene in tactical operations. He is reported to have been angry when Ney organized the French cavalry for the initial charge, but the Emperor was too far away to prevent it. Although Napoleon's presence on the field, according to Wellington, 'was worth 40,000 men' (a statement that could be made equally well of Alexander), at Waterloo he dissipated this effect by remaining too far to the rear. That is a mistake that Alexander could not conceivably have made.

To appreciate the full force of Alexander's achievement we must consider, briefly, what he might have done
against Wellington with the Macedonian army rather than the French. Setting aside the psycological impact on the Macedonian army of exploding gunpowder, it is doubtful that Alexander's army would otherwise have been decisively affected by British firepower. Although Napoleon's forces attacked in even deeper formation than the Macedonian phalanx, and were therefore a more inviting object of attack fir British artillerymen, artillery did not prevent the French from getting within twenty yards of the British line in the fateful final assault. Presumably Alexander's troops might have done that also.

Likewise the infantry musket was not an especially formidable weapon. Useless at 100 yards, it had some
effect at fifty, but the injunction to 'wait until you see the whites of their eyes' was widely applied in Napoleonic warfare, and the Guard had approached to within twenty yards before Wellington turned his own forces against it. At a distance of twenty yards the Macedonian phalanx with its thirteen-foot lances would have been a greater threat to Wellington than Napoleon's Guards. It is of course possible that British firepower might have broken their ranks just as it did, in conjunction with a bayonet charge, against Napoleon's Guard. But a bayonet charge against the Macedonians would have been futile. Since it took several seconds to reload a musket, and the British had only two lines of musketeers, Macedonians within a range of fifty yards or less, trained as they were to charge at the double when necessary, could have closed with devastating effect against the British infantry. Assuming that they could have withstood the initial barrage of fire in which, adittedly, they would have taken heavy losses, Macedonian phalangites would have been vastly superior to British infantrymen in hand-to-hand combat.

Alexander's skirmishers would have been more effective at Waterloo than they were in antiquity. Bows and
slings had a longer effective range than muskets, and, since warriors of the early nineteenth century wore little armour, arrows and slingstones would have done realitively more damage. The likely performance of Macedonian cavalry against British stirrups is perhaps more debatable, but the quality of Macedonian horsemanship was high, and the Macedonian cavalry lance was a fearsome weapon. French lancers caused the British so much trouble on the field at Waterloo that in the following year the British organized their own lancer units.

Obviously one cannot say categorically that Alexander's Macedonian army would have driven Wellington from
his ridge in 1815, but the battle might have been a near-run thing. I am well aware that such comparisons can be odious and have only limited utility. Battles, happily, cannot be refought.