In Deuteronomy are the following orders as to conduct in war:

When thou goest forth to war against thine enemies, and the
Lord thy God hath delivered them into thine hands, and thou
hast taken them captive.

And seest among the captives a beautiful woman, and hast a
desire unto her, that thou wouldest have her to thy wife;
Then thou shalt bring her home to thine house; and she shall
shave her head, and pare her nails;

And she shall put the raiment of her captivity from off her,
and shall remain in thine house, and bewail her father and her
mother a full month: and after that thou shalt go in unto her,
and be her husband, and she shall be thy wife.

And it shall be, if thou have no delight in her, then thou shall
let her go whither she will; but thou shalt not sell her at all
for money, thou shalt not make merchandise of her, because thou
hast humbled her.

The children of Israel, having been sent out by Jahweh to punish the
Midianites, "slew all the males." But Moses was wrath, because they
had spared the women, and he ordered them to kill all the married
women, and to take the single women "for themselves." The Lord
allowed this brutal act--which included the murder of all the male
children--to be consummated. There were sixteen thousand females
spared, of which we are told that "the Lord's tribute was thirty
and two."