Also, I found this at JLaw

Excerpts:

…This approach solves another difficult problem according to Jewish law: the role of the “innocent” civilian in combat. Since the Jewish tradition accepts that civilians (and soldiers who are surrendering) are always entitled to flee from the scene of the battle, it would logically follow that all who remain voluntarily are classified as combatants, since the opportunity to leave is continuously present. Particularly in combination with Joshua’s practice of sending letters of warning in advance of combat, this legal approach limits greatly the role of the doctrine of “innocent civilian” in the Jewish tradition. Essentially, the Jewish tradition feels that innocent civilians should do their very best to remove themselves from the battlefield and those who remain are not so innocent. If one voluntarily stays in a city that is under siege, one has the status of a combatant.50

…In sum, there clearly is a license to wage certain kinds of war and kill certain people in the Jewish tradition. However, in order to exercise this license, one must first seek peace; this peace must be sought prior to declaring war, prior to waging a battle, and prior to laying a siege. While war permits killing, it only permits the intentional killings of combatants. Innocent people must be given every opportunity to remove themselves from the field of combat.

Admittedly, I am not an expert on religious law so if I’m reading this incorrectly, please advise.