Complex sentence: Dupuis was a long time diplomat in the Department of External Affairs and served as Ambassador to the United Nations from 1980 to 1981 and Ambassador to France from 1981 to 1985.
Split into simpler sentences: Dupuis was a long time diplomat in the Department of External Affairs. He served as Ambassador to the United Nations from 1980 to 1981, and Ambassador to France from 1981 to 1985.