I. The inhabitant’s duty to the occupant
As the law ofbelligerent occupation developed out ofthe law which was at one time applicable to conquered territory and ultimately attained an independent status, theories of the nature of the duty owed to the occupant by the inhabitants of the area he occupies have undergone a corresponding change.
Prior to the emergence of a distinct law of belligerent occupation during the second half of the eighteenth century and the early nineteenth century, enemy territory occupied by armed forces immediately became part of the territory of the occupying state. The unqualified allegiance of the inhabitants of the area was, as a matter of course, demanded by the occupant, and their relationship to the occupant was left entirely to municipal law. Thus when Louis XIV took Namur in 1692, the magistrates of the city came to him the next day to render him homage as his loyal subjects. Although there were intimations in the great texts of the seventeenth century that mere belligerent occupation of territory is precarious and that the very uncertainty of the fortunes of war demands restraint in the exercise of belligerent ‘rights’, it remained for Vattel and for Kluber and Heffter in the nineteenth century to assert that sovereignty over an occupied area does not pass to the occupant while hostilities are still in progress. Until a debellatio, normally in the form of a peace treaty, which determines the disposition to be made of the territory, the state whose territory it is is deprived only of the exercise of certain attributes of sovereignty.
The theory that an occupied territory immediately becomes part of the occupying state was slow to die. An English court could state in 1814 that: ‘No point is more clearly settled in the Courts of Common Law than that a conquered country forms immediately part of the King’s dominions.’ In 1875 Sir Travers Twiss still maintained that a belligerent nation taking possession of an enemy’s territory acquires sovereignty over it. A revision of de Martens’ text which was published a decade earlier contains a statement that a state which makes itself master of an enemy province may demand homage from the inhabitants. During the war between the United States and Mexico, General Kearney issued a proclamation absolving all persons residing in the occupied portion of Mexico from their allegiance to that republic and claiming them as citizens of the United States—an act which did not pass without criticism in Congress. However, these are but isolated instances during a period of change. Already, during several wars of the eighteenth century, new theories of belligerent occupation had been given application.  A demand by the occupant for unqualified and permanent allegiance gradually ceased to have the sanction of law or of general practice.
-  Nys, Le Droit international. Lesprincipes, les theories, les faits, vol. iii (1912), p. 223.
-  See, e.g., Wolff, Jus Gentium Methodo Scientifica Pertractatum (1764), § 892; Heffter, Daseuropaische Volkerrecht der Gegenwart (1st ed., 1884), § 132.
-  Van Nispen tot Sevenaer, L’Occupation allemande pendant la derniere guerre mondiale (1946), p. 157.
-  Grotius, De Jure Belli ac Pacis (1625), Book iii, Ch.vi, iv. 1; Pufendorf, De Jure Naturae etGentium Libri Octo (1688), Book viii, Ch. vi, § 7.
-  Vattel, Le Droit des gens (1758), Book iii, Ch.xiii; Kluber, Droit des gens moderne de l’Europe(1831), § 256; Heffter, op. cit., §§ 131—3.
-  TheFoltina (1814), 1 Dods. 450, 451, 165 E.R. 1374, 1375. Cf. The Gerasimo (1857), 11 Moo.P.C. 88, 14 E.R. 628, which indicates that, at least with respect to the question of the enemy characterof occupied territory, the principle enunciated in The Foltina had by 1857 ceased to prevail.
-  The Law of Nations Considered as Independent Political Communities. On the Rights and Duties ofNations in Time of War (2nd ed., 1875), } 64.
-  Precis du droit des gens moderne de l’Europe (2nd ed. by Verge, 1864), } 280.
-  House Executive Document No. 19, 29th Congress, 2nd Session, pp. 20 ff., cited in Thomas,A History of Military Government in Newly Acquired Territory of the United States (1904), p. 104. For acriticism of General Kearney’s conduct, see the remarks of Mr. Holmes in Congressional Globe, 29thCongress, 2nd Session, p. 18.
-  Nys, op. cit., vol. iii, p. 223. A number of historical instances are collected at pp. 227—33.
-  (C.C. Mass. 1815), F. Cas. No. 15,336, 2 Gall. 485.