Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[134] So Saul promised to do what he was commanded; and supposing that his obedience to God would be shown, not only in making war against the Amalekites, but more fully in the readiness and quickness of his proceedings, he made no delay, but immediately gathered together all his forces; and when he had numbered them in Gilgal, he found them to be about four hundred thousand of the Israelites, besides the tribe of Judah, for that tribe contained by itself thirty thousand. Accordingly, Saul made an irruption into the country of the Amalekites, and set many men in several parties in ambush at the river, that so he might not only do them a mischief by open fighting, but might fall upon them unexpectedly in the ways, and might thereby compass them round about, and kill them. And when he had joined battle with the enemy, he beat them; and pursuing them as they fled, he destroyed them all. And when that undertaking had succeeded, according as God had foretold, he set upon the cities of the Amalekites; he besieged them, and took them by force, partly by warlike machines, partly by mines dug under ground, and partly by building walls on the outsides. Some they starved out with famine, and some they gained by other methods; and after all, he betook himself to slay the women and the children, and thought he did not act therein either barbarously or inhumanly; first, because they were enemies whom he thus treated, and, in the next place, because it was done by the command of God, whom it was dangerous not to obey. He also took Agag, the enemies' king, captive, - the beauty and tallness of whose body he admired so much, that he thought him worthy of preservation. Yet was not this done however according to the will of God, but by giving way to human passions, and suffering himself to be moved with an unseasonable commiseration, in a point where it was not safe for him to indulge it; for God hated the nation of the Amalekites to such a degree, that he commanded Saul to have no pity on even those infants which we by nature chiefly compassionate; but Saul preserved their king and governor from the miseries which the Hebrews brought on the people, as if he preferred the fine appearance of the enemy to the memory of what God had sent him about. The multitude were also guilty, together with Saul; for they spared the herds and the flocks, and took them for a prey, when God had commanded they should not spare them. They also carried off with them the rest of their wealth and riches; but if there were any thing that was not worthy of regard, that they destroyed.