Related Rule
United States of America
Practice Relating to Rule 17. Choice of Means and Methods of Warfare
The US Air Force Pamphlet (1976) states:
Those who plan or decide upon an attack must take all feasible precautions in the choice of means and methods of attack with a view to avoiding, and in any event to minimizing, incidental loss of civilian life, injury to civilians, and damage to civilian objects. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 5-3(c)(1)(b)(i)(b).
The US Naval Handbook (1995) states:
The commander must decide, in light of all the facts known or reasonably available to him, including the need to conserve resources and complete the mission successfully, whether to adopt an alternative method of attack, if reasonably available, to reduce civilian casualties and damage. 
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), § 8.1.2.1.
The US Naval Handbook (2007) states:
[T]he commander must decide, in light of all the facts known or reasonably available to him, including the need to conserve resources and complete the mission successfully, whether to adopt an alternative method of attack, if reasonably available, to reduce civilian casualties and damage. 
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, § 8.3.1.
In 1991, during a news briefing concerning the Gulf War, the US Secretary of Defense stated:
Iraq, on the other hand, has chosen to launch a highly inaccurate weapon – the SCUD missile – at major population centers, with no certainty about where the SCUDs will land. In contrast, we have carefully chosen our targets and we’ve bombed them with precision. 
United States, News Briefing by the US Secretary of Defense and the Chairman of the Joint Chiefs of Staff, Washington, 23 January 1991, annexed to Letter dated 25 January 1991 to the President of the UN Security Council, UN Doc. S/22168, 29 January 1991, p. 3.
In 1992, in its final report to Congress on the conduct of the Gulf War, the US Department of Defense stated:
Coalition forces took several steps to minimize the risk of injury to noncombatants. To the degree possible and consistent with allowable risk to aircraft and aircrews, aircraft and munitions were selected so that attacks on targets within populated areas would provide the greatest possible accuracy and the least risk to civilian objects and the civilian population … One reason for the maneuver plan adopted for the ground campaign was that it avoided populated areas, where Coalition and Iraqi civilian casualties and damage to civilian objects necessarily would have been high. This was a factor in deciding against an amphibious assault into Kuwait City … Iraqi units remaining in Kuwait City would cause the Coalition to engage in military operations in urban terrain, a form of fighting that is costly to attacker, defender, innocent civilians, and civilian objects. The decision was made to permit Iraqi forces to leave Kuwait City and engage them in the unpopulated area to the north. 
United States, Department of Defense, Final Report to Congress on the Conduct of the Persian Gulf War, 10 April 1992, Appendix O, The Role of the Law of War, ILM, Vol. 31, 1992, pp. 622 and 643.
In 1993, in its report to Congress on the protection of natural and cultural resources during times of war, the US Department of Defense stated:
A number of steps can be taken by an attacker in order to minimize collateral damage to natural resources or cultural property. Many of these come in the design and development of weapons, weapon systems, and target intelligence, target acquisition, or weapons delivery systems. Each of these systems is enhanced by the quality of training provided [to] personnel responsible for their operation. U.S. efforts to develop, acquire, and utilize weapon systems such as the F-117 aircraft, the laser-guided bomb, and the Tomahawk missile are illustrative of the degree to which the armed services have sought precision in their military operations in order to minimize collateral damage … To the degree possible and consistent with allowable risks to aircraft and aircrews, [during the Gulf War] aircraft and munitions were selected so that attacks on targets in proximity to cultural objects would provide the greatest possible accuracy and the least risk of collateral damage to the cultural property. 
United States, Department of Defense, Report to Congress on International Policies and Procedures Regarding the Protection of Natural and Cultural Resources During Times of War, 19 January 1993, pp. 203 and 205.
In March 2010, in a speech given at the Annual Meeting of the American Society of International Law, the US State Department’s Legal Adviser stated:
Recently, a number of legal objections have been raised against U.S. targeting practices. …
Second, some have challenged the very use of advanced weapons systems, such as unmanned aerial vehicles, for lethal operations. But the rules that govern targeting do not turn on the type of weapon system used, and there is no prohibition under the laws of war on the use of technologically advanced weapons systems in armed conflict – such as pilotless aircraft or so-called smart bombs – so long as they are employed in conformity with applicable laws of war. Indeed, using such advanced technologies can ensure both that the best intelligence is available for planning operations and that civilian casualties are minimized in carrying out such operations.
Third, some have argued that the use of lethal force against specific individuals fails to provide adequate process and thus constitutes unlawful extrajudicial killing. But a state that is engaged in an armed conflict or in legitimate self-defense is not required to provide targets with legal process before the state may use lethal force. Our procedures and practices for identifying lawful targets are extremely robust, and advanced technologies have helped to make our targeting even more precise. In my experience, the principles of distinction and proportionality that the United States applies are not just recited at meetings. They are implemented rigorously throughout the planning and execution of lethal operations to ensure that such operations are conducted in accordance with all applicable law. 
United States, “The Obama Administration and International Law”, Speech given by the Legal Adviser of the US Department of State at the Annual Meeting of the American Society of International Law, Washington DC, 25 March 2010.
[emphasis in original]