Understanding the nature of military occupation, both from the perspective of an observer and from the perspective of a participant, is difficult because military occupation as a political phenomenon displays in acute form a tension that is at the heart of many concepts in political life. It is a phenomenon that is shaped both by the normative features that define it at one level, above all by the idea that the occupant enjoys authority but is not sovereign, and the factual features that establish it, above all by the military force that stands behind government by the occupant. It is a phenomenon that cannot be reduced to one or the other of these two sets of features, as if one were the essence of the phenomenon and the other were contingent. Shorn of the defining qualification of the exercise of authority without the right of sovereignty, government backed by force could as well be an instance of conquest, or even in at least some measure the ordinary condition of government. Without the factual exercise of authority the claim to military occupation too readily looks at best like an entirely spurious claim and at worst like a sinister strategy to deprive opponents of the status of legitimate belligerency, though occupants have often stepped back from that conclusion, as had the British and the Italians towards the end of the long nineteenth century.

The necessity of the relationship between the two in order for the phenomenon of military occupation to be meaningful was implicit, and sometimes fairly explicit, in the arguments of contemporaries, especially when occupation seemed to be slipping, usually by intention, into conquest and the assertion of sovereignty. Bosnia-Herzegovina, Cyprus and Egypt all seemed to be cases where the retention of the claim to sovereignty by the ousted sovereign seemed less and less plausible as the occupant showed no sign of imminent departure, as the occupant's claims took on increasingly normative form and the factual power became more pervasive. That was the inevitable inverse of the dependency of the claim to sovereignty of the legitimate power upon some factual condition, albeit one which is put in danger by the very fact of occupation.