Related Rule
United States of America
Practice Relating to Rule 112. Search for and Collection of the Dead
The US Field Manual (1956) reproduces Article 15 of the 1949 Geneva Convention I. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 216.
The US Air Force Pamphlet (1976) refers to Article 15 of the 1949 Geneva Convention I. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 12-2(a).
The US Operational Law Handbook (1993) states: “The LOW [law of war] requires Parties to a conflict to search for the dead”. 
United States, Operational Law Handbook, JA 422, Center for Law and Military Operations and International Law Division, The Judge Advocate General’s School, United States Army, Charlottesville, Virginia 22903-1781, 1993, p. Q-185.
The Annotated Supplement to the US Naval Handbook (1997) provides that the requirement for parties to the conflict, after each engagement and without delay, to take all possible measures to search for and collect the wounded and sick “also extends to the dead”. 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 11.4, footnote 19.
The US Naval Handbook (2007) states: “As far as military exigencies permit, after each [naval] engagement all possible measures should be taken without delay to search for … and to recover the dead.” 
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, § 8.6.1.
The US Manual on Detainee Operations (2008) states:
Legal Considerations
a. As a subset of military operations, detainee operations must comply with the law of war during all armed conflicts, however such conflicts are characterized, and in all other military operations …
c. The four Geneva Conventions of 1949 are fully applicable as a matter of international law to all military operations that qualify as international armed conflicts … The principles reflected in these treaties are considered customary international law, binding on all nations during international armed conflict. Although often referred to collectively as the “Geneva Conventions,” the specific treaties are:
(1) [1949] Geneva Convention [I] … This convention … provides for the collection of dead persons. 
United States, Manual on Detainee Operations, Joint Chiefs of Staff, 30 May 2008, pp. I-2–I-3.
In 1987, the Deputy Legal Adviser of the US Department of State affirmed: “We support … the principle that each party to a conflict permit teams to search for … and recover the dead from the battlefield.” 
United States, Remarks of Michael J. Matheson, Deputy Legal Adviser, US Department of State, The Sixth Annual American Red Cross-Washington College of Law Conference on International Humanitarian Law: A Workshop on Customary International Law and the 1977 Protocols Additional to the 1949 Geneva Conventions, American University Journal of International Law and Policy, Vol. 2, 1987, p. 424.
According to the Report on US Practice, it is the opinio juris of the United States that all possible measures should be taken to search for the dead. 
Report on US Practice, 1997, Chapter 5.1.