Related Rule
United States of America
Practice Relating to Rule 84. The Protection of Civilians and Civilian Objects from the Effects of Incendiary Weapons
The US Rules of Engagement for Vietnam (1971) stated: “The use of incendiary type munitions in inhabited or urban areas will be avoided unless friendly survival is at stake or it is necessary for the accomplishment of the commander’s mission.” 
United States, Rules of Engagement for the Employment of Firepower in the Republic of Viet-Nam, US Military Assistance Command Viet-Nam, Directive No. 525-13, May 1971, unclassified contents reprinted in Eleanor C. McDowell, Digest of United States Practice in International Law, 1975, US Department of State Publication 8865, Washington, D.C., 1976, pp. 814–815, § 6(d)(1).
The US Air Force Pamphlet (1976) states:
The potential of fire to spread beyond the immediate target area has also raised concerns about uncontrollable or indiscriminate effects affecting the civilian population or civilian objects. Accordingly, any applicable rules of engagement relating to incendiary weapons must be followed closely to avoid controversy. The manner in which incendiary weapons are employed is also regulated by the other principles and rules regulating armed force … In particular, the potential capacity of fire to spread must be considered in relation to the rules protecting civilians and civilian objects … For example, incendiary weapons should be avoided in urban areas, to the extent that other weapons are available and as effective. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 6-6(c).
The US Naval Handbook (1995) states:
Incendiary devices such as tracer ammunition, thermite bombs, flame throwers, napalm, and other incendiary weapons and agents, are lawful weapons. Where incendiary devices are the weapons of choice, they should be employed in a manner that does not cause incidental injury or collateral damage that is excessive in light of the military advantage anticipated by the attack. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Transportation, US Coast Guard, October 1995 (formerly NWP 9 (Rev. A)/FMFM 1-10, October 1989), § 9.7.
The US Naval Handbook (2007) states:
Incendiary devices, such as thermite bombs, flame throwers, napalm, and other incendiary weapons and agents, are lawful weapons. Where incendiary devices are the weapons of choice, they should be employed in a manner that does not cause incidental injury or collateral damage that is excessive in light of the military advantage anticipated by the attack. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 9.8.
In 2008, the US Senate approved the ratification of the 1980 Protocol III to the Convention on Certain Conventional Weapons, subject to a reservation, an understanding and a declaration:
SECTION 1. SENATE ADVICE AND CONSENT SUBJECT TO A RESERVATION, AN UNDERSTANDING, AND A DECLARATION
The Senate advises and consents to the ratification of the Protocol on Prohibitions or Restrictions on the Use of Incendiary Weapons to the Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May be Deemed to be Excessively Injurious or to Have Indiscriminate Effects (Protocol III), adopted at Geneva on October 10, 1980 (Treaty Doc. 105-1(B)), subject to the reservation of section 2, the understanding of section 3, and the declaration of section 4.
SECTION 2. RESERVATION
The advice and consent of the Senate under section 1 is subject to the following reservation, which shall be included in the instrument of ratification:
The United States of America, with reference to Article 2, paragraphs 2 and 3, reserves the right to use incendiary weapons against military objectives located in concentrations of civilians where it is judged that such use would cause fewer casualties and/or less collateral damage than alternative weapons, but in so doing will take all feasible precautions with a view to limiting the incendiary effects to the military objective and to avoiding, and in any event to minimizing, incidental loss of civilian life, injury to civilians and damage to civilian objects.
SECTION 3. UNDERSTANDING
The advice and consent of the Senate under section 1 is subject to the following understanding, which shall be included in the instrument of ratification:
It is the understanding of the United States of America that any decision by any military commander, military personnel, or any other person responsible for planning, authorizing or executing military action shall only be judged on the basis of that person’s assessment of the information reasonably available to the person at the time the person planned, authorized, or executed the action under review, and shall not be judged on the basis of information that comes to light after the action under review was taken.
SECTION 4. DECLARATION
The advice and consent of the Senate under section 1 is subject to the following declaration:
This Protocol is self-executing. This Protocol does not confer private rights enforceable in United States courts. 
United States, Advice and consent to ratification of the 1980 Protocol III to the Convention on Certain Conventional Weapons, 2008, Sections 1–4.
In 1976, during discussions in the Ad Hoc Committee on Conventional Weapons established by the CDDH, the representative of the United States stated:
36. … The United States delegation could not accept any proposal which would have the effect of precluding the use of napalm or similar weapons in close-combat situations. It could therefore not accept total prohibition of the use of such weapons or prohibition of their anti-personnel use.
37. Her delegation recognized, however, that special limitations were appropriate in areas populated by civilians. It had carefully studied the proposal in the working paper submitted to the Lugano Conference [of Government Experts on the Use of Certain Conventional Weapons] by the Netherlands experts and introduced again in the Ad Hoc Committee [as an annex to a working paper, see supra] that the use of air delivered flame weapons should be prohibited in populated areas, except for the zone in which combat between ground forces was taking place or was imminent. Such a prohibition would preclude the use of air-delivered napalm against military targets in cities, towns or villages, such as ammunition and supply dumps, vehicle parks, convoys and barracks. Acceptance of that proposal would involve the abandonment of lawful uses of napalm against legitimate military targets. In view, however, of the concern that the use of air-delivered napalm in populated areas might prove dangerous to civilians, the United States delegation was prepared to accept the Netherlands proposal as a basis for serious negotiation, and was also prepared to consider any other proposals for protecting the civilian population from the effects of incendiary weapons. 
United States, Statement at the CDDH, Official Records, Vol. XVI, CDDH/IV/SR.27, 19 May 1976, p. 281, §§ 36–37.
At the Preparatory Conference for the Convention on Certain Conventional Weapons in 1979, the United States explained that it
could not accept a total ban on the use of incendiary weapons, because the weapons substituted for them would, in certain situations, be more destructive and consequently more injurious, and would thus be contrary to the spirit of article 57 of the Protocol on International Armed Conflict [Additional Protocol I].
The United States went on to say that, while it could not accept a restriction on the use of incendiaries against combatants,
an agreement on limiting the use of incendiaries in areas containing civilian concentrations was appropriate and possible … The [Australia/Netherlands] proposal was the maximum that some of the principal interested parties at the Conference would be prepared to accept. 
United States, Statement at the Preparatory Conference for the Convention on Certain Conventional Weapons, UN Doc. A/CONF.95/PREP.CONF/II/ SR.28, 18 April 1979, pp. 2–3, §§ 5–6.
With respect to the decision by the United States whether or not to use incendiary weapons during a strategic bombing campaign against North Korean industrial areas during the Korean War, it is reported:
At the Target Selection Committee meeting General Weyland pointed out that someone would have to decide whether or not the B-29’s could use incendiary munitions, and within a few days FEAF [Far Eastern Air Force] got the answer to this question – in the negative. Washington was very hesitant about any air action which might be exploited by Communist propaganda and desired no unnecessary civilian casualties which might result from fire raids. General Stratemeyer consequently directed General O’Donnell not to employ incendiaries without specific approval. 
Robert F. Futrell, The US Air Force in Korea 1950–1953, Office of Air Force History, US Air Force, Washington, D.C., Revised edition, 1983, p. 187.
In transmitting the Protocols to the 1980 Convention on Certain Conventional Weapons to the US Senate, the US President stated:
The United States must retain its ability to employ incendiaries to hold high priority military targets such as those at risk in a manner consistent with the principle of proportionality which governs the use of all weapons under existing law. 
United States, Message from the US President transmitting Protocols II, III and IV to the Convention on Certain Conventional Weapons to the Senate for consent to ratification, Treaty Doc. 105-1, Washington, 7 January 1997, Tab (B), p. 4.
In November 2005, the US Department of Defense issued a transcript of a news briefing given jointly by the US Secretary of Defense Donald H. Rumsfeld and the Chairman, Joint Chiefs of Staff, Gen. Peter Pace, regarding the war in Iraq. The following extract from the transcript relates to the use of incendiary weapons:
Q: [Referring to a recent article in the New York Times] But in its final paragraph or so, it takes particular issue with the use of white phosphorus in urban areas. And based on what we have learned so far, have you banned the use of “Willy Pete” or are you considering banning it? Or will it continue to be used?
SEC. RUMSFELD: General Pace.
GEN. PACE: White phosphorus is a legitimate tool of the military. It is used for two primary purposes. One is to mark a location for strike by an aircraft, for example. The other is to be used – because it does create white smoke – to be used as a screening agent so that you can move your forces without being seen by the enemy.
It is not a chemical weapon, it is an incendiary (sic) [The transcript added a statement: “It is not an incendiary weapon as defined by the 1980 Convention on Certain Conventional Weapons”], and it is well within the law of war to use those weapons as they are being used for marking and for screening.
Q: But you and I have both seen the results of “Willy Pete” in Vietnam. And when it’s on the skin, it doesn’t stop burning until it goes all the way through or runs out of oxygen. It’s a pretty tough weapon. Do you want to use it in urban areas such as Fallujah?
GEN. PACE: No armed force in the world goes to greater effort than your armed force to protect civilians and to be very precise in the way we apply our power. A bullet goes through skin even faster than white phosphorus does. So I would rather have the proper instrument applied at the proper time as precisely as possible to get the job done in a way that kills as many of the bad guys as possible and does as little collateral damage as possible. That is just the nature of warfare. 
United States, Department of Defense, Office of the Assistant Secretary of Defense (Public Affairs), News Transcript, News Briefing with Secretary of Defense Donald Rumsfeld and Gen. Peter Pace, 29 November 2005.