Jerome A. Brentar was born in 1922 in northern Ohio, the son of immigrants from Croatia. During the Second World War he served in Europe with the US Army's 93rd Armored Cavalry. From 1948 to 1950, he worked in postwar Europe as an eligibility/screening officer for the International Refugee Organization (IRO) of the United Nations. From 1954 to 1957 he worked in Europe for the Catholic Relief Service of the National Catholic Welfare Conference, a Roman Catholic refugee assistance agency. Besides English and Croatian, Brentar speaks German, Polish, Russian and Ukrainian. He studied at Michigan State University and at the University of Munich in Germany. Back in Ohio, he founded and for many years directed Europa Travel Service, a travel agency in Cleveland.