The US-backed Kosovovian (?) terrorist group that actually started the war is blameless, of course. And it's not outrageous for NATO- an organisation formed for the sole purpose of protecting Germany the Russians, an organisation that was supposed to disband after 1991- carried out the bombing. Nup. All Serbia's fault.
NATO didn't carry out acts of genocide. Serbia did.
Act of genocide, actually. There was only one major act of genocide from Serbia- the Srebrenica Massacre is the pretty much the only major act of genocide predating NATO involvement.
The war, as I recall, was started by Croatia trying to break out of being part of Yugoslavia, then Serbia deciding they didn't want that.
The (later) war in Kosovo, at least, was certainly started by the KLA, acting to try to ethnically cleanse what they regarded as their land. In the words of the US Committee for Refugees, the KLA "attacks aimed at trying to 'cleanse Kosovo of its ethnic Serb population'.
The Yugoslav Red Cross: "Over 90 mixed villages in Kosovo have now been emptied of Serb inhabitants and other Serbs continue leaving, either to be displaced in other parts of Kosovo or fleeing into central Serbia. ”
And even Nato admitted that the KLA was "the main initiator of the violence" launching "what appears to be a deliberate campaign of provocation".
(all from wiki, here
http://en.wikipedia.org/wiki/Kosovo_Liberation_Army#First_attacks)
After police stations, government buildings and civilians had been targeted by the KLA terrorists, the Serbs understandably over-reacted in response. NATO, in particular Germany, strongly backed the KLA, perhaps as early as 1996. So Germany and, later, the US acted to support a genocidal terrorist group with a heavy bombing campaign of it's victims.
After the KLA took over a reasonably sizable region of the country, the government tried to reestablish control. NATO responded with 'air shows', eventually leading to bombing. NATO opposed any peace agreement that was not essentially an unconditional surrender by the government- where the government would promise to stop maintaining order, and the terrorist group would retain their weapons, continue attacks, continue ethnic cleansing and so on.
After the government refused this absurd and impossible demand, NATO made good on it's repeated threat to turn Yugoslavia into a 'smoking ruin', to 'lay waste to Belgrade' and so on, bombing flat much of the country including deliberately-chosen civilian targets (media centres, for example). Remember that the justification for this bombing campaign was that the government refused to give in to terrorists- they were probably even willing to negotiate, though not with thee absurd preconditions set by NATO.
As predicted, violence against civilians escalated by both sides after the NATO bombing campaign, the usual result of such bombing.
Ultimately, the NATO/KLA alliance was victorious, and the former terrorists now run the 'country'- which has been cleansed of most of it's Serbian population.