Warren Zimmermann, diplomat and outspoken humanitarian, who has died aged 69 of pancreatic cancer, was the last US ambassador to Yugoslavia before its disintegration into civil war.
He had served with distinction in Moscow (1973-75 and 1981-84), Paris, Caracas and Vienna, where he headed the US delegation at the Conference on Security and Co-operation in Europe (1986-89).
But it was Yugoslavia that marked him more than any other phase in his professional life and brought him to prominence as a public servant prepared to stand up for the cause in which he believed.
Zimmermann resigned from the diplomatic service in 1994 in protest at President Bill Clinton's reluctance to intervene in the Bosnian war; but he did not leave matters there. He campaigned ceaselessly to persuade the US that it must act to end Serbian aggression in the killing fields of Bosnia and wrote a perceptive, and deeply moving, account of his experiences in Yugoslavia, The Origins Of A Catastrophe (1996). He went on to teach at Johns Hopkins University (1994-96) and Columbia University (1996-2000) and lost no opportunity to speak out against human rights violations and the search for justice in the Balkans.
President George Bush snr appointed Zimmermann to Yugoslavia in 1989, when the first stirrings of the break-up of the federation were making themselves felt. His brief was to support the federal government in Belgrade against the forces promoting ethnic strife, and for a considerable time - in common with other Western diplomats - he thought self-interest and the economic fabric of Yugoslavia were strong enough to withstand assault from within.
Up to 1991 Zimmermann was still telling visiting journalists he was confident Yugoslavia would stick together as a unified country.
But the evidence to the contrary was mounting steadily. Serbian President Slobodan Milosevic's nationalism was fuelling more and more violence. Zimmermann was appalled by the mounting crisis, but failed to convince Washington that forceful action was imperative if Serb aggression was to be curbed. All that Bush was prepared to do by way of protest was to recall his ambassador to Washington in 1992; he was appointed to direct the State Department's bureau of refugee programmes.
When Zimmermann saw Bush's successor, Clinton, also resisting calls for military intervention, he decided he had no alternative but to resign from government service to gain the freedom to condemn the administration's prevarication and argue for a principled stand against the ethnic cleansing. It took Clinton another year to finally endorse NATO intervention. Though vindicated, Zimmermann felt Western military involvement had come much too late, and at the cost of many lives that could have been saved.
In Origins of a Catastrophe, Zimmermann condemned the inaction. "Western diplomacy was reduced to a kind of cynical theatre, a pretence of useful activity, a way of disguising a lack of will. Diplomacy without force became an unloaded weapon, impotent and ridiculous," he wrote.
Recalling Zimmermann's achievements, the US Secretary of State, Colin Powell, singled him out as an eloquent defender of human rights, and the former senior US diplomat, Arthur Hartman, with whom Zimmermann worked in three postings, described him as "the fellow who always brought us back to the human dimension of the job".
Zimmermann came from an established Philadelphia family and grew up in Haverford, Pennsylvania. He studied literature at Yale and won a Fulbright scholarship to read history at Cambridge University. He joined the US foreign service in 1961.
He was a fly fisherman and spent summers at a cottage he owned on Glandore Harbour on the coast of Co Cork, where he enjoyed taking extended walks.
Warm-hearted and always deeply committed to human rights, he forged lasting friendships in the countries where he served and was daring in cultivating dissidents during his postings in the Soviet Union. His interest in history was also long-standing, and his second book, First Great Triumph: How Five Americans Made Their Country A World Power (2002), examined the Spanish-American war.
His wife, Corinne, was his supportive partner and helped to make their home in Virginia a haven both for refugees from persecution and for their many friends. She and their two daughters and a son survive him.
Warren Zimmermann: born November 16th, 1934; died February 3rd, 2004