Rwanda

So...
A couple of months ago, the Marine Corps Command and Staff College embarked on a study of Rwanda. An example of a peacekeeping mission that went as wrong -- I hope -- as it's possible to go.

Simplistic overview: Rwanda is inhabited by two major peoples (or tribes, if you'd prefer), the Hutu and Tutsi. Hutus are the majority. Tutsi are ethnically similar, but are often physically larger and were chosen by the colonial power of Belgium to be the dominant peoples.

After independence, along with wheels within wheels, various forms of fighting developed between the two. After many missteps and fumbles and the beginning of civil war, the UN injected a peacekeeping force under the command of a Canadian General named Dallaire (also a graduate of the US Marine Corps Command and Staff College).

Dallaire was tipped off to a plot to slaughter Tutsis, made a plan to confiscate the equipment, advised his chain of command, and was ordered not to proceed.

The massacre started with the death of the president of Rwanda in a plane crash -- actually the a/c was shot down. At its height, the killers were murdering more per hour than the Nazis did during WWII. In about 100 days, about 800,000 people were killed.
1. If Rwanda had never been a colony, the Hutu and Tutsi would be, at worst, tribes that don't like each other and occasionally go to war.
2. If the UN had done nothing, the civil war would have fought itself out. Tragedy? Yes. Massacre? Probably no.
3. If the population had been armed, the killers would have been considerably more circumspect.
Here's a review of a book on the subject: http://www.bookslut.com/nonfiction/2005_07_005966.php