Richard Holbrooke's arrival in the Balkans in 1995 was a transformative moment - the moment the Americans seized control of the peace process from the Europeans and intervened decisively to end the war in Bosnia.
US diplomats had grown openly contemptuous of British and French efforts to broker a peace agreement between Serb separatists and the mainly Muslim (but multi-ethnic) Bosnian government.
Countless "peace plans" had been drawn up and time after time it was the Bosnian Serbs from their mountain capital Pale near Sarajevo who rejected those plans, choosing instead to carry on with war as a way of carving out an ethnically pure Serbian state in Bosnia.
American diplomats at that time spoke with heartfelt outrage not just about the war but about the huge criminal enterprise known as "ethnic cleansing".
Madeleine Albright, then US ambassador to the UN, blamed the Europeans for pursuing a policy of appeasement towards the Serbs that reminded her of British Prime Minister Neville Chamberlain's capitulation to Hitler at Munich in 1938. She wanted international action to halt and reverse Serb military gains.
It fell to Richard Holbrooke to come up with a way of doing it.
The Europeans, by contrast, had peacekeepers on the ground - British, French, Nordic and other so-called blue helmets - struggling to bring humanitarian aid to the dispossessed and the besieged.
They were peacekeepers with no peace to keep. European governments, fearing for the safety of their troops on the ground, seemed reluctant to blame anyone until all sides could be blamed equally. As the war went on and on, American officials came to condemn what they saw as the timidity and ineffectiveness of European policy.
Richard Holbrooke believed that the European approach demonstrated that humanitarian aid alone could prolong a war without changing its outcome. He argued for something more robust.
Ending the killing
Two things changed fundamentally when Holbrooke took the leadership of the peace process. First, he was ready to apportion blame to one side more than the others. Second, his was a policy predicated on a readiness to use military force.
The Europeans argued that this approach would endanger their troops. Holbrooke replied that in that case they should withdraw.
The Europeans resisted this. One British commander in Bosnia began to brief reporters that military intervention could prove disastrous - that the Americans were about to cross what he called the "Mogadishu line" that separated peacekeeping from war-fighting.
So Holbrooke not only took on Slobodan Milosevic and his Bosnian Serb proxies, he also took on sceptical and, at times, hostile allies in Europe.
Nato did, in the end, intervene militarily. Several weeks of sustained aerial bombardment in the summer and autumn of 1995 reversed many of the Serbs' territorial gains and threatened to roll them back altogether.
Faced for the first time with a military opponent they could not overcome, the Serbs went to the negotiating table. Holbrooke locked the parties in at Dayton air force base and forbade them to make any public statements until an agreement had been reached.
Within weeks the war was over. Bosnians had agreed to a new post-war constitution that divided the country into two "entities" - one Serb, the other shared between Bosnia's other two main ethnic groups, the Croats and Muslim Bosniaks.
Fifteen years on that constitution is still in force. Its critics say it has in effect dismembered Bosnia and made the central government so weak that the institutions of statehood have never taken root.
But Dayton ended more than three-and-a-half years of killing - and that was Richard Holbrooke's achievement.