In 1962 he became a research scientist at the Institute of History of Socialistic Countries of Slovak Academy of Sciences.
In the first part of his career (until half of 80's), he was focused on research of foreign policy issues of Central European states and Yugoslavia in the interwar period (1918-1939).
He held various functions in scientific organisations, including positions in bilateral international commissions of historians.
He did extensive consultation and expert work for public authorities and civil society organizations.
President of Slovak republic awarded him in memoriam with Ľudovít Štúr Order - class I. for a special merit and a lifetime contribution to the development of culture, particularly in the field of historical sciences.