Plutarch, Alexander
Bernadotte Perrin, Ed.

11. Thus it was that at the age of twenty years Alexander received the kingdom, which was exposed to great jealousies, dire hatreds, and dangers on every hand. For the neighbouring tribes of Barbarians would not tolerate their servitude, and longed for their hereditary kingdoms; and as for Greece, although Philip had conquered her in the field, he had not had time enough to make her tame under his yoke, but had merely disturbed and changed the condition of affairs there, and then left them in a great surge and commotion, owing to the strangeness of the situation. [2] The Macedonian counsellors of Alexander had fears of the crisis, and thought he should give up the Greek states altogether and use no more compulsion there, and that he should call the revolting Barbarians back to their allegiance by mild measures and try to arrest the first symptoms of their revolutions; but he himself set out from opposite principles to win security and safety for his realm by boldness and a lofty spirit, assured that, were he seen to abate his dignity even but a little, all his enemies would set upon him. [3] Accordingly, he put a speedy stop to the disturbances and wars among the Barbarians by overrunning their territories with an army as far as to the river Danube, where he fought a great battle with Syrmus, the king of the Triballi, and defeated him; and on learning that the Thebans had revolted and that the Athenians were in sympathy with them, he immediately led his forces through the pass of Thermopylae, declaring that since Demosthenes had called him a boy while he was among the Illyrians and Triballians, and a stripling when he had reached Thessaly, he wished to show him that before the walls of Athens he was a man.

[4] Arrived before Thebes, ¹ and wishing to give her still a chance to repent of what she had done, he merely demanded the surrender of Phoenix and Prothytes, and proclaimed an amnesty for those who came over to his side. But the Thebans made a counter-demand that he should surrender to them Philotas and Antipater, and made a counter-proclamation that all who wished to help in setting Greece free should range themselves with them; and so Alexander set his Macedonians to the work of war. [5] On the part of the Thebans, then, the struggle was carried on with a spirit and valour beyond their powers, since they were arrayed against an enemy who was many times more numerous than they; but when the Macedonian garrison also, leaving the citadel of the Cadmeia, fell upon them in the rear, most of them were surrounded, and fell in the battle itself and their city was taken, plundered, and razed to the ground. This was done, in the main, because Alexander expected that the Greeks would be terrified by so great a disaster and cower down in quiet, but apart from this, he also plumed himself on gratifying the complaints of his allies; for the Phocians and Plataeans had denounced the Thebans. [6] So after separating out the priests, all who were guest-friends of the Macedonians, the descendants of Pindar, ² and those who had voted against the revolt, he sold the rest into slavery, and they proved to be more than thirty thousand; those who had been slain were more than six thousand.