Attachment 4


A4.1. Introduction. During planning, targeting personnel must contend with two external sources of

restrictions on weapons and target selection. First, and most basic, are the constraints imposed by international

law. Second are other constraints imposed by higher headquarters for military or political reasons.

This attachment concerns itself solely with the restrictions on weapons and targeting imposed by

international law.

A4.2. General Restrictions on Air Bombardment: The Immunity of Civilians.

A4.2.1. Protection of the Civilian Population and Civilian Objects. The civilian population as

such, as well as individual civilians, may not be made the object of attack. Acts of violence intended

primarily to spread terror among the civilian population are prohibited. Neither may civilian property

that is not a military objective be the object of attack.

A4.2.1.1. Non-participation in Hostilities . Civilian immunity carries with a strict obligation on

the part of civilians not to take a direct part in hostilities--they must not become combatants. Taking

a direct part in hostilities means engaging in acts of war directed toward enemy personnel or

materiel. Civilians who take part in fighting (whether singly or as a member of a group) become

combatants and lose their personal immunity.

A4.2.1.2. Requirement to Distinguish . The requirement to distinguish between combatants

and civilians and between military objectives and civilian objects imposes obligations on all the

parties to a conflict. This is true whatever the legal status of the territory on or over which combat

occurs. For example, civilians may not be used in an attempt to render an area immune from military

operations. Also, civilians may not be used to shield a defensive position, to hide military

objectives, or to screen an attack. Neither may they be forced to leave their homes or shelters in

order to disrupt the movement of an adversary.

A4.2.2. Military Objectives. Military attacks must be directed only against military objectives. Military

objectives are those objects which by their nature, location, purpose, or use make an effective

contribution to military action and whose total or partial destruction, capture, or neutralization in the

circumstances offers a definite military advantage.

A4.2.2.1. Many objects are clearly military objectives --for example, the enemy’s military

encampments or armament (such as military aircraft, tanks, antiaircraft emplacements, and troops

in the field). Factories, workshops, and plants that directly support the needs of the enemy’s armed

forces are also generally conceded to be legitimate military objectives.

A4.2.2.2. Controversy exists over whether, and under what circumstances, other objects such as

civilian transportation and communications systems, dams, and dikes can properly be classified as

military objectives. Modern transportation and communications systems are deemed military

objectives because they are used heavily for military purposes in intense conflicts.

A4.2.2.3. However, the inherent nature of an object is not controlling. Even a traditionally civilian

object (such as a civilian house) can be a military objective when it is occupied and used by

military forces during an armed engagement. The key factor is whether the object makes an effec-

tive contribution to the adversary’s military action, so that its capture, destruction, or neutralization

offers a definite military advantage in the circumstances ruling at the time.

A4.3. Precautions in Attack. Only a military objective is a lawful object of attack. Therefore, constant

care must be taken when conducting military operations to spare nonmilitary objects and persons, and

positive steps must be taken to avoid or minimize any civilian casualties or damage. The principle of proportionality

must always be followed, which prohibits an attack when the expected collateral civilian

casualties or damage to civilian objects is excessive or disproportionate to the military advantage anticipated

by the attack.

A4.3.1. Types of Precautions. The extent of danger to the civilian population varies with the type of

military objective attacked, the type of terrain, the type of weapons used, the kind of weather, and

whether civilians are nearby. It also depends on the combatant’s ability and mastery of bombardment

techniques, the level of the conflict, and the type of resistance encountered during the attack. Therefore

the following steps must be taken:

A4.3.1.1. Identification of Military Objectives . Initially, those who plan or decide upon an

attack must do everything feasible under the specific circumstances at the time to ensure military

objectives, and not civilians or civilian objects, are in fact being attacked. Sound target intelligence

enhances military effectiveness by showing that the risks undertaken are militarily worthwhile.

A4.3.1.2. Incidental Civilian Casualties Must Be Minimized . Attacks are not prohibited

against military objectives even though they may cause incidental injury or damage to civilians.

In spite of precautions, such incidental casualties are inevitable during armed conflict.

• This incidental injury or damage must not outweigh the expected direct military advantage.

That is, the potential military advantage must be balanced against the probable

degree of incidental injury or damage to civilians. If an attack is carried out efficiently,

using the principle of economy of force, against a military installation, it would not be

likely to violate this rule.

• On the other hand, if the attack were directed against objects used mainly by the civilian

population in an urban area (even though they might also be military objectives), its military

benefits would have to be carefully weighed against the risks to civilians.

• Required precautionary measures are reinforced by traditional military doctrines, such as

economy of force, concentration of effort, target selection for maximization of military

advantage, avoidance of excessive collateral damage, accuracy of targeting, and conservation

of resources.

A4.3.1.3. Cancellation or Suspense of Attacks in Case of Mistake . Target intelligence may

be found to be faulty before an attack is started or completed. If it is apparent that a given target

is not a military objective, or that the target is under the special protection of international law, the

attack must be canceled or suspended. An example of such special protection would be a hospital

protected under the 1949 Geneva Conventions.

A4.3.1.4. Warning Requirement . Under the Hague Regulations, a warning must be given prior

to bombardment, when circumstances permit, to permit the civilian population an opportunity to

avoid injury. The "Hague Rules", written at the Hague Peace Conference of 1907, deal largely

with how to fight an enemy who is in the field, and is still fighting, while the Geneva Conventions

deal chiefly with the respect due our enemy, who is no longer able to fight, as well as treatment of

civilians and civilian objects. If civilians are unlikely to be affected by the attack, the warnings

need not be given. A general warning may satisfy this requirement, because a specific alert could

jeopardize the attack force or the mission.

A4.3.2. Prohibition of Attack on Undefended Areas. Under the Hague Regulations, towns, villages,

dwellings, or buildings that are undefended may not be attacked or bombarded. An undefended

place is any inhabited place near, or in, a zone where opposing armed forces are in contact, and which

is open for occupation by an adverse party without resistance.

A4.4. Separation of Military Activities.

A4.4.1. International law generally gives civilians "immunity" from attack during armed conflict.

However, the parties to a conflict must also take all the precautions practical to protect their own civilian

population, individual civilians, and civilian objects. For example, they should remove civilians

from military objectives and avoid locating military objectives in or near densely populated areas.

A4.4.1.1. Under the 1949 Geneva Conventions, safety zones or demilitarized zones may be created

between the parties of the conflict. Although the creation of such zones is unlikely if past

experience is any indication, if created they would be an effective measure to enhance protection

of a state's own civilian population.

A4.4.1.2. Under these rules, persons who are combatants are required to wear uniforms, and facilities

such as hospitals should be clearly marked. Similarly, international law also requires belligerents

to locate military objectives away from hospitals and not to use civilians to shield military

objectives from attack.

A4.4.2. Result of Failure to Separate Military Activities. A state’s failure to segregate and separate

its own military activities and to avoid placing military objectives in or near a populated area may

greatly weaken protection of its civilian population. Such protection is also compromised when civilians

take a direct part in hostilities or are used unlawfully in an attempt to shield attacks against military

objectives .

A4.5. Special Protection. In additional to the general rules for protecting civilians and civilian populations,

there are specific rules for protecting certain persons and facilities. Under the 1949 Geneva Conventions,

the following persons and objects must be protected from attack:

A4.5.1. Wounded and Sick, Medical Units and Hospitals, and Medical Means of Transport.

• Hospitals and other fixed or mobile medical establishments.

• Medical personnel and chaplains.

• Medical transport.

• Medical aircraft, when flying at agreed times on agreed routes.

• Hospital ships and, to the extent possible, sick bays of warships.

• Wounded, sick and shipwrecked persons must not knowingly be attacked, fired upon, or

unnecessarily prevented from discharging their proper function. However, the incidental

injury of personnel or damage to objects that are at, or near, a military target which is being

attacked by fire, gives no just cause for complaint.

A4.5.2. Religious, Cultural, and Charitable Buildings and Monuments. Because they are not

used for military purposes, buildings devoted to religion, art or charitable purposes, as well as historical

monuments, may not be made the object of air bombardment. However, combatants have a duty

to identify such places with distinctive and visible signs. When such buildings are used for military

purposes, they may qualify as military objectives and may be attacked. Lawful military objectives are

not immune from attack because they are located near such buildings, but all possible precautions

must be taken to spare the protected buildings.

A4.5.3. Prisoner of War (PW) Camps. Prisoners of war may not be the object of attack. They may

not be kept in a combat zone or used to render an area immune from military operations. When military

considerations allow it, prisoner of war camps are identified by the letters "PW" or "PG" placed

so they are clearly visible from the air. The use of PW camp markings for any other purpose is prohibited.

A4.6. Weapons: The Distinction Between an Unlawful Weapon and Unlawful Use of a Weapon.

International law may prohibit completely the use of a specific weapon or may prohibit a specific use. A

weapon is illegal per se if international law has forbidden its use in all circumstances. Poison as a gas, as

a coating on munitions, or as a contaminant of water is an example of such an illegal weapon. However,

any weapon may be used unlawfully; for example, firing a rifle at civilians or at combatants who have surrendered.

A4.7. General Principles Applicable to Weapons.

A4.7.1. Unnecessary Suffering. It is forbidden to employ any method or weapon of warfare which

causes superfluous injury or unnecessary suffering. This firmly established rule, incorporated into the

Hague Regulations, is a concrete expression of the general principles of proportionality and humanity.

All weapons cause suffering. Whether particular weapons or methods of warfare cause unnecessary

suffering (and hence are unlawful per se) is best determined by the practice of states. The critical factor

is whether the weapon has been designed, or is used, so that it will cause suffering or aggravation

of wounds as a separate element in the attack, and not the degree of suffering itself. Treaties banning

specific weapons, such as gas and toxin weapons, also give specific content to this principle. The rule

against unnecessary suffering also prohibits the infliction of suffering for its own sake, or for mere

indulgence in cruelty. International law has condemned the use of expanding bullets against combatants

and determined that it is illegal per se to use:

• Projectiles filled with glass or other materials inherently difficult to detect medically

• Any substance on projectiles that tends unnecessarily to inflame the wound they cause

• Irregularly shaped bullets. It is illegal to score the surface, or file off the ends of the hard

cases, of bullets, so that they will expand upon contact and thus aggravate the wound they


A4.7.2. Indiscriminate Weapons. The law of armed conflict also prohibits the use of any weapon

that cannot be directed at a military target. However, a weapon is not unlawful simply because its use

may cause incidental civilian casualties. An indiscriminate weapon is one that cannot be controlled,

through design or function. Some weapons are considered indiscriminate because, although they can

be directed at a military objective, they may have otherwise uncontrollable effects that cause disproportionate

civilian injuries or damage. Biological weapons are an example.

A4.8. Biological and Chemical Weapons.

A4.8.1. Biological Weapons. International law prohibits the use of biological weapons or methods

of warfare. These weapons are also prohibited by the 1972 Convention of the Prohibition of the

Development, Production, and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on

their Destruction. The US, along with many other states, is party to this treaty.

A4.8.2. Chemical Weapons. The 1993 Convention on the Prohibition of the Development, Production,

Stockpiling, and Use of Chemical Weapons And on Their Destruction (Chemical Weapons Convention),

entered into force on 29 April 1997 and bans the use of chemical weapons as a method of

warfare. The Chemical Weapons Convention corrects a shortfall in the 1925 Geneva Protocol for the

Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases and of Bacteriological

Methods of Warfare, which prohibits the use of chemical weapons in combat, but not their development,

production, stockpiling or transfer.

A4.8.3. Herbicides and Riot Control Agents. US policy on herbicides and riot control agents in

war is set forth in an Executive Order: The United States renounces, as a matter of national policy,

first use of herbicides in war except use, under regulations applicable to their domestic use, for control

of vegetation within US bases and installations or around their immediate defensive perimeters and

first use of riot control agents in war except in defensive military modes to save lives, such as:

• Use of riot control agents in riot situations in areas under direct and distinct US military control,

to include controlling rioting prisoners of war.

• Use of riot control agents in situations in which civilians are used to mask or screen attacks

and civilian casualties can be reduced or avoided.

• Use of riot control agents in rescue missions in remotely isolated areas, of downed aircrews

and passengers, and escaping prisoners.

• Use of riot control agents in rear echelon areas outside the zone of immediate combat to protect

convoys from civil disturbances, terrorists, and paramilitary organizations. The Secretary

of Defense shall take all necessary measures to ensure that the use of riot control agents and

chemical herbicides in war by US Armed Forces is prohibited unless such use has Presidential

approval in advance. Executive Order Number 11850, 8 April 1975. The Chemical Weapons

Convention bans the use of riot control agents as a method of warfare. However, the use of

riot control agents permitted under Executive Order 11850 has been deemed consistent with

the Chemical Weapons Convention since the listed uses are not considered ‘as a method of


A4.8.4. Poison. Article 23(a) of the Hague Regulations forbids states to employ poison or poisoned

weapons. The prohibition against poison is based on its uncontrolled character, on the fact that it is

inevitably disabling or fatal, and on the traditional belief that it is treacherous to use poison.

A4.9. Nuclear Weapons. The US does not regard the use of explosive nuclear weapons, whether by air,

sea, or land forces, as a violation of existing international law. Nuclear weapons can be directed against

military objectives as can conventional weapons. However, the authority of United States forces to

employ nuclear weapons resides solely with the President. Moreover, the United States is a party to

numerous treaties that regulate the use of nuclear devices. Some examples are the Additional Protocol II

to the Treaty for the Prohibition of Nuclear Weapons in Latin America, the Outer Space Treaty, and a

treaty prohibiting nuclear weapons on the seabed.

A4.10. Conventional Weapons and Weapons Systems.

A4.10.1. Aircraft, Rockets, and Guided Missiles. The use of aircraft, rockets, and guided missiles

by land, sea, or air forces against combatants and other lawful military objectives is clearly permissible.

A4.10.2. Fragmentation Weapons. The use of explosives and fragmentation particles, such as those

contained in projectiles, mines, bombs, rockets, missiles, and hand grenades, is not prohibited under

the law of armed conflict. Cluster bomb units, a more recent development in warfare, are only a

refinement or special type of fragmentation munition.

A4.10.3. Incendiary Weapons. Incendiary weapons, such as incendiary ammunition, flame throwers,

napalm, and other incendiary agents, have widespread uses in armed conflict. They are clearly

regarded as lawful in situations requiring their use. Any controversy over their use arises from a concern

for the medical problem in treating burn injuries and from arbitrary attempts to analogize their

use to the use of prohibited means of chemical warfare. The potential danger of spreading fire has

also raised concerns about civilian protection. Their use should be avoided in urban areas, to the

extent that other weapons are available and are equally effective.

A4.10.4. Delayed Action Weapons. Air-dropped mines and other delayed action weapons are legal.

However, mines are unlawfully used when they are attached as booby traps to any object that is protected

under international law, such as to wounded and sick personnel, dead bodies, or medical facilities.

Also objectionable are portable booby traps, such as fountain pens, watches, and trinkets, that

would expose any civilians who might be attracted to the object, to an injury. Mines must not be used

to prevent the rescue of wounded and sick persons, or to deny civilians protection. Under the Hague

Convention VIII, there are specific treaty restrictions on the use of mines in sea warfare.