text: General Background and Basic Principles of the Law of Armed Conflict
  will come from higher authority regarding which rule set may apply; but, if no such guidance is forthcoming,
  commanders must adhere to the LOAC rules for State-on-State conflict described in paragraph 1-14 below.
  1-9. War may be described as the existence of armed hostility between States, between States and non-State
  armed groups, or between non-State armed groups, although the specific legal definition of “war” may
  depend on the legal purpose at issue (see DOD Law of War Manual, 1.5). For example, under the U.S.
  Constitution, Congress has the power to declare war, which it last did formally in World War II. Of course,
  the United States has often engaged in armed conflict or “war,” under international law, since that time, often
  with congressional support or authorization. Even if parties involved in hostilities do not refer to such actions
  as “war” or “armed conflict,” LOAC applies to the hostilities at issue. For this reason, and because the terms
  “war” and “armed conflict” often are used interchangeably, this manual uses them as synonyms.
  1-10. Whether a LOAC rule applies may depend on whether a war exists. Jus in bello treaties often provide
  that they apply to cases of “declared war or of any other armed conflict,” even if a state of war is not
  recognized by the parties (see Common Article 2, the Geneva Conventions of 1949). This standard has also
  been understood to result in the application of the customary law of war. A case of “declared war or any other
  armed conflict” for the purpose of determining whether parties must comply with jus in bello rules may be
  understood as arising in two ways: (1) when a party intends to conduct hostilities; or (2) when parties are
  actually conducting hostilities. What specific parts of LOAC apply as a matter of law to a given war may
  depend on whether the war is characterized as an international armed conflict (IAC) or a non-international
  armed conflict (NIAC).
  EXISTENCE OF A WAR FOR PURPOSES OF APPLYING THE LAW OF ARMED CONFLICT
  1-11. Whether an armed conflict exists for the purpose of applying LOAC may be an intent-based analysis.
  If States or non-State armed groups seek to engage in armed conflict, they are bound by LOAC with respect
  to the conduct of hostilities and the protection of war victims (see DOD Law of War Manual, 3.4.1). As such,
  LOAC obligations must be taken into account even before the fighting actually begins, such as in the planning
  of military operations.
  1-12. Whether an armed conflict exists may also be a conduct-based analysis. Armed conflict may exist
  absent a declaration of war or without the participating States acknowledging they are engaged in armed
  conflict. The factual existence of an armed conflict is sufficient to trigger LOAC obligations for the conduct
  of hostilities and the protection of war victims.
  1-13. A helpful rule of thumb may be that where parties are, in fact, engaged in activities that LOAC
  contemplates (including detention of enemy military personnel without criminal charge, or bombardment of
  military objectives), those activities are subject to LOAC.
  INTERNATIONAL ARMED CONFLICT
  1-14. An international armed conflict (IAC) refers to any declared war between States, or to any other
  armed conflict between States, even if the state of war is not recognized by one of them. The Geneva
  Conventions apply to all cases of international armed conflict and all cases of partial or total occupation of a
  territory, even if the occupation meets no armed resistance (Common Article 2 to Geneva Convention for the
  Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field [GWS], Geneva
  Convention for the Amelioration of the Condition of Wounded, Sick, and Shipwrecked Members of Armed
  Forces at Sea [GWS Sea], Geneva Convention Relative to the Treatment of Prisoners of War [GPW], and
  Geneva Convention Relative to the Protection of Civilian Persons in Time of War [GC]). Other law of war
  treaties also generally apply to international armed conflict and occupation (such as Hague Convention (IV)
  Respecting the Laws and Customs of War on Land [Hague IV], and its Annex: Regulation Concerning the
  Laws and Customs of War on Land (The Hague, October 18, 1907) [HR]). The United States has interpreted
  “armed conflict” in Common Article 2 of the 1949 Geneva Conventions to include any situation in which
  there is hostile action between the armed forces of two parties, regardless of the duration, intensity, or scope
  of the fighting (see DOD Law of War Manual, 3.4.2).