Deuteronomy 20:10-15

10When thou comest near to a city to fight against it, then proclaim peace to it. 11And it shall be, if it shall make thee answer of peace, and open to thee, then it shall be, that all the people that are found in it shall be forced labourers to thee, and they shall serve thee. 12And if it will make no peace with thee, but will make war against thee, then thou shalt besiege it: 13And when the LORD thy God hath delivered it into thy hands, thou shalt smite every male of it with the edge of the sword: 14But the women, and the little ones, and the cattle, and all that is in the city, even all the spoil of it, shalt thou take to thyself; and thou shalt eat the spoil of thy enemies, which the LORD thy God hath given thee.1 15Thus shalt thou do to all the cities which are very distant from thee, which are not of the cities of these nations.