Mr William Walker, the American head of the international observer mission to Kosovo who was expelled by Yugoslavia yesterday, is a veteran diplomat well versed in the political minefield of the Balkans.
He had a 37-year career in the US Foreign Service and most recently served as head of the UN Transitional Administration for Eastern Slavonia (UNTAES) in Croatia.
Mr Walker also served as deputy assistant secretary of state from 1985 to 1988 and ambassador to El Salvador from 1988 to 1992.
As head of the mission to Kosovo, which was co-ordinated by the Organisation for Security and Co-operation in Europe (OSCE), he was charged with verifying that Yugoslavia kept its promise to end its crackdown on Kosovo's ethnic Albanian majority.
On his appointment, Mr Giancarlo Aragona, the OSCE Secretary-General, said: "Ambassador Walker, thanks to his overall diplomatic experience, which is impressive, and his knowledge of former Yugoslavia at large, is certainly a very suitable head of mission."
In an interview before he took over the OSCE mission, Mr Walker described the hand-over of eastern Slavonia from UN administration to Croatia as "a model of a successful UN operation with a clear mandate, a timetable, appropriate forces and a single chain of command".
After Belgrade ordered Mr Walker's expulsion, the current OSCE chairman condemned the Yugoslav government's decision.
"This act is totally unacceptable. It may put the whole OSCE mission in jeopardy," the Norwegian Foreign Minister, Mr Knut Vollebaek, said.
"President Slobodan Milosevic has challenged the whole international community . . . It may lead to increased violence in Kosovo."