Perhaps it really is, ultimately, simple and obvious. Perhaps confronting violence with more violence cannot lead to peace, just as common sense tells us it doesn't reduce violence. Perhaps there is no place for the force of arms in modern international diplomacy, and if the community of nations cannot prevent a thuggish despot from killing and oppressing his neighbors or his own people by persuasion and negotiation, they should not attempt to do so by coercion. Perhaps.
But I remain, frankly, unconvinced. Just because we've seen major powers and the international organizations they form to implement extra-national diplomacy misuse their military power, using international laws and treaties, along with explanations of humanitarian intentions to justify the imposition of a specific agenda by force, or even to provide political and diplomatic cover for aggressive warfare. And certainly there have been other cases, where the intent was good but the execution got caught up in political and military struggles to assert power that led to disasters like Somalia. But the idealist in me continues to insist that with reasonably pure motives and a limited set of goals, the international community can come together to protect a helpless population from dictators, warlords and criminals for whom their lives are worth, at most, the cost of a bullet.
First, let's be clear. Vietnam, Afghanistan and Iraq were in no way humanitarian interventions. They were essentially unilateral aggressive wars fought out of choice for entirely political reasons. Korea and Gulf War I were arguably fought for good reasons, but Korea was mismanaged into a years long bloodbath where millions lost their lives and livelihoods, and while Gulf War I was perhaps the best example of how to fight a twenty-first century war, the aftermath descended into political acrimony, economic manipulation, murderous sanctions and thus became a festering regional open sore, driving political factions to increasingly brutal and radical positions for reasons that literally had nothing to do with Iraq itself.
Somalia was a poor choice for humanitarian intervention, because there was no political or even tribal or religious infrastructure to facilitate the delivery of food and medicine. Remember, the intervention in Somalia was not originally intended to be a fight, but rather a mechanism to bring about a temporary end to the bloodshed and the delivery of desperately needed aid. But it was the armed forces that were tapped to provide the relief services, and militaries tend to be uncomfortable with missions that do not primarily involve breaking things and hurting people, so the mission slowly and inevitably evolved into a combat role, and all hope of a good outcome was gone in a 24 hour paroxysm of bloodletting.
Bosnia was a good example of what humanitarian intervention could have been. But confusion, uncertainty, incompetence and outright cowardice left the good people promised a safe haven in Srebrenica occupying mass graves, and everything after that, despite a surprisingly good marketing campaign, turned forever to ashes.
So far, I think it is completely fair to see Libya as a success. A strictly interpreted no-fly zone would have been the worst combination of intervention and ineffectiveness, but working as both the strategic and tactical air force for the Rebels has leveled the playing field and allowed the Rebels time to organize while the Gaddhafi loyalists could read the writing on the wall and decide to change sides. There is no doubt that had the world not intervened, Gaddhafi's air, armor, heavy weapons and superior firepower would have quickly doomed the rebellion, and the fall of Misrata and later Benghazi would have been horrific, brutal massacres of the first order. So the intervention in Libya has met the key criterion for humanitarian military intervention - the minimal force required to change the combat dynamic so the bad guy loses, while being prepared to kill members of either side in sufficient numbers if they threaten non combatants. It certainly remains to be seen what the outcome and disengagement will look like, but so far it's pretty easy to see Libya as a successful operation.
I would have been prepared to support intervention in Rwanda and Sudan, but it seems that industrial scale murder and rape of civilians is necessary, but not sufficient to cause the international community, particularly the US and Europe, to act. In a cynical moment, one might observe that in order to qualify for humanitarian intervention, a nation either needs to be populated by white Europeans, or have significant natural resources, particularly oil reserves. This may or may not be exclusively true, as the sample size is necessarily small, but it obviously must be considered at least a contributing factor. But one Ranger Battalion with sufficient air mobility could have saved hundreds of thousands of lives in Rwanda, and al-Bashir could have been coerced to moderate his behavior and control the paramilitaries by holding some of his more treasured assets at risk.