Joshua took all these royal cities and their kings and put them to the sword. He totally destroyed them, as Moses the servant of the LORD had commanded. Yet Israel did not burn any of the cities built on their mounds—except Hazor, which Joshua burned. The Israelites carried off for themselves all the plunder and livestock of these cities, but all the people they put to the sword until they completely destroyed them, not sparing anyone that breathed. As the LORD commanded his servant Moses, so Moses commanded Joshua, and Joshua did it; he left nothing undone of all that the LORD commanded Moses.Josh. 11:12-15. Now, Alexander's conquest seems generally limited to defeating armies rather than razing cities, but there is at least one exception. Here is how Plutarch recounts the defeat of Thebes.
The Thebans indeed defended themselves with a zeal and courage beyond their strength, being much outnumbered by their enemies. But when the Macedonian garrison sallied out upon them from the citadel, they were so hemmed in on all sides that the greater part of them fell in the battle; the city itself being taken by storm, was sacked and razed. Alexander's hope being that so severe an example might terrify the rest of Greece into obedience, and also in order to gratify the hostility of his confederates, the Phocians and Plataeans. So that, except the priests, and some few who had heretofore been the friends and connections of the Macedonians, the family of the poet Pindar, and those who were known to have opposed the public vote for the war, all the rest, to the number of thirty thousand, were publicly sold for slaves; and it is computed that upwards of six thousand were put to the sword.Full selection. The thing is, Alexander is reported as feeling great guilt of his treatment of Thebes. So much so that he attributed "the unwillingness of the Macedonians to follow him against the Indians, by which his enterprise and glory was left imperfect, to the wrath and vengeance of Bacchus, the protector of Thebes." Of course, there is no reason to take either author at face value. I think it is fair to assume that both authors are intended to exault their subjects. It seems likely to me that Plutarch felt that Alexander would be well served by a compassionate image, while the author of Joshua felt that Joshua would be well served by an image of unflinching resolve. I wonder if there are any obvious reasons for the differences.