The path of Humanitarian Intervention/3rd Generation Peacekeeping(aka Peace Enforcement aka War)/Responsibility-to-Protect (R2P) is the path of madness. It is a path with no means of restraining itself, of stepping back and saying 'maybe we shouldn't."
Responsibility to protect will always justify further effort. The person who says 'we should overthrow Rwanda, Libya, Iraq, and Mali, but not Eritrea' will always be less virtuous in their Responsibility to Protect over the person who says 'all of the above but lets also invade Eritrea'. There is no such thing as a bridge too far. At least, not intellectually. Those making decisions about where to act will not act with infinite manpower and willpower. But because of this 'failure to act', there will always be behind them the drumbeats of 'do more'. 'Rwanda is done but what about Eritrea? Eritrea is done but what about Liberia. What about Cuba. What about Haiti. and here. and there. and there.' It's not a slippery slope, it's a mere extension of the same logic. And it never ends.
And yet intervention presumes effectiveness. People like Samantha Power really do think in terms of 'if we just acted we would have lost a few dozen and saved hundreds of thousands in Rwanda.' but lets take a different look.
After 100k dead by Faction A on Faction B, the United States intervenes. In the beginning the violence escalates even faster as people try to finish feuds before it gets to be too late. Toll:150k. Initially the US presence enforces order. No one knows how to continue the fighting during the day. But at night when the troops go back to barracks the kidnappings begin. Neighbors re-escalate away from prying eyes. Meanwhile Faction B is alive. In our original timeline they are devastated in the initial waves of violence and have to retreat out of the country, destined to lick their wounds and vow revenge but never confident enough in their probability of winning that they restart the violence.
But in our intervention timeline that violence is stopped and they are able to reconstitute. The US didn't pick a winner. It merely stopped the violence. And now that the element of surprise is gone now and Faction B knows whats going to happen. One day the US will leave and the violence will return. So it's only logical to act now before Faction A is even more prepared. They smuggle in guns to replace their machetes and make plans. At night the violence starts anew, only this time it's Faction B hitting Faction A. A mixed neighborhood becomes entirely Faction B. Toll 175k.
The US can't figure out how to stop the violence. It enforces good order during the day but it can't be everywhere at once. There is a debate in the US about doubling the number of troops from 20k to 40k. This debate will take a month to resolve in congress.
By the end of the month the toll is 200k. A minority religious group, only 2% of the population, that was neither Faction A nor Faction B, and was there since 200AD has been cleansed. Their presence gone forever. They made the mistake of picking neither side and so both sides killed them just in case they defected to the other side. In the initial timeline the violence never touched them, Faction A just killed Faction B. But in the more intense neighborhood fighting that results from the US presence not allowing one side to win they are just gone.
It's burning up now.
The tit for tat escalates. Former army members are bringing training and professionalism to what were previously gang fights. In the beginning the US didn't even have a map of the city. Now it clearly labels areas as no-go zones because it's prestigious to kill US troops. It proves your military mettle to you fellow Faction-ists. No one listens to calls for peace. No one ever wanted peace. Each side wanted to Win and the US stopped them. One month later the toll is now 300k.
The violence spreads to the countryside where no amount of patrolling can keep an eye on everyone. 500k.
The US has finally figured out the name and organizational structure of one of the largest among the hilariously innumerable groups. It will target their top dog first. As a result a more ruthless and effective leaders rises up the ranks. The military didn't realize that they actually killed an older respected leader who made restricted decisions. In his stead is now a 32 year old ethnic fanatic respected by the group not for his legacy but for his reputation of effectiveness and ruthlessness. He's a Rwandan Nathan Bedford Forrest. Someone who climbed from nowhere up the ranks mindbogglingly quick. He's a madman full of hate just like everyone else, but unlike everyone else (including the former leader) he knows how to fight effectively. He declares that the US strike was proof that they need to act even faster and harder and that they will take back Area X as proof that Faction B will never disappear like that minority group did under the dastardly hands of Faction A.
The toll is 700k and the drums have settled to an uncomfortably steady beat. More and more. Like a Shepards Tone the war seems to be this unending morass of escalation yet each day is numerically similar to the last.
https://www.youtube.com/watch?v=BzNzgsAE4F0&t=52s
After four more months of this the death toll starts getting argued about whether it's 800k or 1 million. Wonks start using mathematical models to predict where it will be one year from now. The US continues to call for peace while trying to build infrastructure to 'win hearts and minds'. An interesting proposal is brought up. Maybe we can stop the violence by hiring the militia of one faction and sticking them somewhere where they won't do any harm. This idea is incredibly controversial in the US as it involves literally putting fanatic murderers we were just trying to stamp out onto the US payroll. It's implemented anyways as a test case. Wonks point out that, despite the political fallout, since implementation the rate of killings has decreased. After further killings, bribes, and incorporation into a convoluted payment structure meant to avoid responsibility in case someone defects back to terrorism, the US manages to reduce the killings to a low simmer and declares victory.
Final death toll: 1.3 million and ongoing. Faction A and Faction B are both still alive and have merely put their militias behind a veil of 'we don't need you right now but stay ready just in case'
And the capital city that started like this
https://gulf2000.columbia.edu/images/maps/Baghdad_Ethnic_2003_lg.jpg
becomes this
https://i.imgur.com/MTDLVzR.jpg
That's an ethnic map of Baghdad from 2003 followed by 2006-2007. Because the alternate history I told was literally just the story of Baghdad. Because after all that military intervention, infrastructure building, and conciliation efforts in the name of peacekeeping what brought peace wasn't effort by an external power. It wasn't the Surge, or Democracy, or decapitations of the leaders of militant groups. It wasn't even the hiring program where the US literally paid/bribed former adversaries to be 'totally legit' and 'definitely on our side at least until we stop paying them'.
It was when the fight over mixed neighborhoods resulted in a Shia victory. They cleansed all the mixed neighborhoods of Sunni's and the Sunni's retreated and concentrated enough that the Shia advance was halted and a Balance of Power was formed.
And only once that balance of power was achieved did both sides agree to form a Westphalian Peace. "Cuius regio, eius religio." Whose realm, their religion.
But because the US intervened and became responsible for the entire debacle we'll never know the counterfactual that if we had just stayed out and let one side win it would have resulted in 500k less deaths.
Meanwhile back in the US Samantha Power when asked whether the decision to get involved in Rwanda was right says the following
"Imagine how many more would have died if we hadn't intervened"
and then the press conference turns to Gaddafi in Libya. And the madness never. ever. ends.