What constitutes war? Andrew Stigler and I point out some of the difficulties in coming up with standards:
Should a 40-minute raid conducted by several dozen commandos be regarded as "hostilities" commensurate with an act of war? After all, force was projected across borders and without the permission of the host government. But if not, how many soldiers must be involved to cross the threshold between "military action" and "war"? How long must they be engaged?
No matter how reasonable, any answer to these questions will have a degree of arbitrariness. Political science does not offer much help. One of the more common academic definitions of war comes from the Correlates of War project, which collects scientific data on wars. It defines war as a conflict in which there are 1,000 battlefield deaths. The figure is clearly arbitrary. The Falklands War, with 907 deaths, does not qualify as a war, while the less consequential 100-hour-long "Soccer War" between El Salvador and Honduras, with about 2,000 fatalities, does.
Writing at World Politics Review, Thomas Weiss argues that we have crossed a threshold: Indeed, until the international action in Libya, R2P often constituted a barrier to deploying military force for human protection. In the aftermath of Libya, we are over that hump." In so doing, we are witnessing a change in the international norms on the use of force.
Robert Jackson observes that the UN resolution authorizing action in Libya (UN Sec Res 1973) "constitutes an expansion of the right of war in international relations"--moving away from self-defense and preserving peace in favor of permitting intervention in the "domestic jurisdictions of sovereign nations that present no threat to their neighbors or to international peace." [Other contributors to the World Politics Review special issue include Daniel Larison and Heather Hurlburt.]
All of this will further muddy the question of "what war is."