In particular the following principles are usually emphasized: force should only be considered a measure of"last resort" after all other peaceful means have been exhausted; force should only be used in "proportion" to the objective, which is generally interpreted to mean that only the minimum level of force should be used in a carefully calibrated fashion; and that it should be applied "discriminately" to minimize unnecessary death and destruction especially to innocent civilians.
These guiding principles are on the surface appealing but in practice difficult to observe. Thus, what constitutes "last resort" is clearly a subjective matter. Extending the search for peaceful or non-violent solutions can also be morally questionable since it may prolong the suffering of innocent victims. Early uses of force, on the other hand, can―if effective―forestall further violence. As German scholar Hanns Maull observed well before these issues surfaced during the Kosovo conflict "using force in pursuit of international order under certain circumstances will argue for early and perhaps even rather massive use of military force―in analogy to domestic politics, where nobody would argue that the police should interfere only as a last resort, and with minimum strength."48 Indeed, the general principles of domestic law enforcement that have been accepted in several UN agreements, do not stress that force should be used as a last resort and in a sparing fashion. Rather it is generally recognized that while non-violent means should be explored where they appear to offer a solution, the circumstances of the situation should ultimately determine the timing of and the extent to which deadly force is employed.
Judging from much of the commentary on the Kosovo operation, there is growing acceptance that force cannot be a measure of last resort. As Smith and Naim argue: "the global community cannot relegate the use of force to the option of last resort. Effective prevention, and particularly deterrence, require a readiness to use force when it will do the most good, not just when it is least inconvenient or politically inescapable" (emphasis added).49 Many believe, for example, that this would have prevented the genocide in Rwanda.50
The fifth and final source of friction centers on the managerial questions relating to the use of force. Organizing, assembling, and controlling an ad hoc group of national armed forces for collective enforcement missions has repeatedly represented a major challenge that on many occasions has undermined or diluted the effectiveness of these kinds of operations. It is the reason why the original architects of the United Nations called for member nations to hold forces "immediately available" for "combined international enforcement action" under the direction of the Military Staff Committee (Article 45). While this never materialized, the general idea has been resurrected since the end of the cold war in the form of various proposals to create a standing UN rapid reaction force to act in emergencies and as a vanguard for larger deployments.51 However, these proposals have for a variety of reasons never progressed beyond the conceptual stage. This is unfortunate as there are compelling arguments in favor of creating a relatively small and mobile force that can act in a timely manner to deter and prevent particular situations from deteriorating. Again the experience of domestic law enforcement suggests that a little policing in the fight place at the fight time can go a long way.
