Civilian casualties Civilian casualties is a military term describing civilian persons killed , injured , or imprisoned by military action . Civilian casualties can be associated with the outcome of any form of military action regardless of whether civilians were targeted directly or not . This differs from collateral damage which specifically applies to only unintentional effects of military action including unintended casualties . Some researchers have included refugees and internally displaced persons in their definition of " civilian casualty " . Civilian casualties therefore include victims of atrocities such as the Nanking Massacre committed on a civilian population where hundreds of thousands of men were slaughtered , while girls and women ages ranging from 10 to 70 were systematically raped and / or killed by Japan ese soldiers in 1937 . Another example is the My Lai Massacre ( ) that was committed by United States soldiers during the Vietnam War on hundreds of unarmed Vietnamese civilians . Such military action , which has the sole purpose of inflicting civilian casualties , is illegal under modern rules of war , and may be considered a war crime or crime against humanity . Other kinds of civilian casualties may involve the targeting of civilian populations for military purposes , such as the atomic bombings of Hiroshima and Nagasaki , which killed over 150 , 000 people , although both cities contained major military installations and factories which were dispersed within civilian areas . The legality of such action was at the time governed by international law found in the 1907 Hague Regulations on Land Warfare , which states that " the attack or bombardment , by whatever means , of towns , villages , dwellings , or buildings which are undefended is prohibited . " Also relevant , were the Hague Rules of Air Warfare of 1922 – 1923 , which states that " an air bombardment is legitimate only when is directed against a military objective , i . e . an objective whereof the total or partial destruction would constitute an obvious military advantage for the belligerent " , although the document was never adopted in a legally binding form . The Rome Statute defines that " intentionally directing attacks against the civilian population " to be illegal , but only came into effect on July 1 , 2002 and has not been ratified by every country . The ethics of civilian casualties . Many modern nations ' views on the ethics of civilian casualties align with the Just War theory , which advocates a system of proportionality . An act of war is deemed proportional in Just War theory if the overall destruction expected from the use of force is outweighed by the projected good to be achieved . This view is a war - adapted version of utilitarianism , the moral system which advocates that the morally correct action is the one that does the most good . However , moral philosophers often contest this approach to war . Such theorists advocate absolutism , which holds there are various ethical rules that are , as the name implies , absolute . One such rule is that non - combatants cannot be attacked because they are , by definition , not partaking in combat ; to attack non - combatants anyway , regardless of the expected outcome , is to deny them agency . Thus , by the absolutist view , only combatants can be attacked . The philosopher Thomas Nagel advocates this abolutist rule in his essay " War and Massacre " . Finally , the approach of pacifism is the belief that war of any kind is morally unjust . Pacifists sometimes extend humanitarian concern not just to enemy civilians but also to combatants , especially conscripts . Civilian casualty ratio . The civilian casualty ratio in an armed conflict is the ratio of civilian casualties to combatant casualties or total casualties . The measurement can apply either to casualties inflicted by a particular belligerent or to casualties in the conflict as a whole . The ratio of ten civilian casualties for every combatant is a frequently - cited , but disputed figure .