Short answers, pulled from the story.
Oskar Halecki (the 26th of May 1891 - the 17th of September 1973) was a Polish historian, Catholic activist, and professor who advanced the concept of East Central Europe as a distinct historical region. He taught at Fordham University, Columbia University, and the University of Montreal, and led the Polish Institute of Arts and Sciences in America from 1952 to 1964.
Halecki argued that Eastern Europe, distinct from Russia, was no less European than Western Europe, and that both shared the same spiritual ideals and cultural traditions as part of one European community. His work contributed to the gradual acceptance of the concept and name of East Central Europe as a scholarly category.
Halecki's magnum opus was a two-volume history of the Jagiellonian Union, published in 1919 and 1920. He also worked extensively on a biography of Jadwiga of Anjou, which was published two decades after his death in 1973.
After Germany invaded Poland in 1939, Halecki went to Paris, where he organised the Polish University in Exile, taught at the Sorbonne, and edited the emigre periodical La Voix de Varsovie. When France fell in 1940, he escaped to the United States with help from Stephen Mizwa and the Kosciuszko Foundation, and later taught at Vassar College and Fordham University.
In 1966, Halecki received the Polish American Historical Association's first Haiman Award for outstanding contributions to Polish American studies. After his death, the association established the Halecki Prize in 1981, given to recognise an important book or monograph on the Polish experience in the United States.
In 1921, Halecki joined the League of Nations Secretariat in Geneva and spent three years organising its Committee on Intellectual Co-operation. He then served as Chief of the University Section in the league's Institute on Intellectual Co-operation in Paris, working across its various commissions for several years.