Deuteronomy 20:10-12 NIV

10 When you march up to attack a city, make its people an offer of peace.1

References for Deuteronomy 20:10

11 If they accept and open their gates, all the people in it shall be subject2 to forced labor3 and shall work for you.

References for Deuteronomy 20:11

12 If they refuse to make peace and they engage you in battle, lay siege to that city.