DEPARTMENTOFDEFENSE LAW OFWARMANUAL JUNE2015

applied. 65 The limited and unreliable nature of information available during war also is
recognized in the law of war’s standards for how persons are to assess information. 66
1.5 “WAR” AS A LEGAL CONCEPT
“War” is sometimes used as a legal concept, i.e., the application or operation of a legal
rule may depend on the existence of a “war,” “armed conflict,” or “hostilities.” As a legal
concept, “war” has traditionally been viewed as a condition in which a State is prosecuting its
rights by military force, usually against another State. However, the precise definition of “war”
often depends on the specific legal context in which it is used.
1.5.1 Traditional Conception of War Under International Law. As international law
began to regulate “war,” “hostilities,” and “armed conflict,” it became necessary to determine
what “war” is for the purpose of triggering those legal obligations. 67
As a legal concept, war has usually been described as a condition or state that applies
more broadly than only the mere employment of force or the mere commission of acts of
violence. 68
When treated as a legal concept, “war” has been associated with a State’s use of force to
vindicate its rights (principally, its inherent right of self-defense) under international law. 69
65 Refer to § 2.2.3 (Applying Military Necessity).
66 Refer to § 5.4 (Assessing Information Under the Law of War).
67 See, e.g., Arnold D. McNair, The Legal Meaning of War, and the Relation of War to Reprisals, 11 TRANSACTIONS
OF THE GROTIUS SOCIETY 29, 30 (1925) (“There exist many treaties and other international conventions under which
important obligations arise upon the occurrence of a state of ‘war,’ and as regards which, therefore, either because
the term ‘war’ or some other term connoting war, such as ‘neutrality,’ is used, it becomes essential to know whether
or not a state of war exists at a given point of time. Thus most of the Hague Conventions only come into operation
once a state of war has arisen—for instance, those relating to the Laws and Customs of War on Land, to the Rights
and Duties of Neutrals in Land and Maritime War respectively, to the Bombardment of Ports, Towns and Villages
by Naval Forces, and to the Status of Enemy Merchant Ships at the Outbreak of Hostilities.”).
68 1956 FM 27-10 (Change No. 1 1976) 8 (“While it is usually accompanied by the commission of acts of violence,
a state of war may exist prior to or subsequent to the use of force.”); VII MOORE’S DIGEST 153 (“Much confusion
may be avoided by bearing in mind the fact that by the term war is meant not the mere employment of force, but the
existence of the legal condition of things in which rights are or may be prosecuted by force.”); GROTIUS, LAW OF
WAR & PEACE 33 (1.1.2.1) (“war is the condition of those contending by force”).
69 SPAIGHT, AIR POWER AND WAR RIGHTS 2 (“War, after all, is only a means to an end. It is a way of settling an
international difference which diplomacy has failed to adjust and which is not susceptible of treatment by the other
means of pacific settlement, such as inquiry commissions, arbitration, or submission to the Permanent Court of The
Hague. When all else fails, there is no way in which a nation can assert its rights save by going to war. War is the
means by which it vindicates a vital right threatened or infringed by the claim or act of another State. Its object is to
cause the other State to desist from the action or abandon the claim which is the cause of offence. In other words, a
war is fought in order to bring about a change of mind in another State.”); The Prize Cases, 67 U.S. 635, 666 (1863)
(“War has been well defined to be, ‘That state in which a nation prosecutes its right by force.’”) (quoting EMERICH
DE VATTEL, DROIT DE GENS (LAW OF NATIONS) (1760)); LIEBER CODE art. 30 (“Ever since the formation and
coexistence of modern nations, and ever since wars have become great national wars, war has come to be
acknowledged not to be its own end, but the means to obtain great ends of state, or to consist in defense against
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