He came from a landowning family and was born in the village of Czyszki, near Sambir, as a son of Marian Jan Andrzej and Helena Kunegunda (nee Kotarski). In 1908 he completed secondary school at the Scientific and Educational Department of the Jesuit Fathers in Chyrów, where he received the final certificate with distinction. In 1908 he took up studies at the Department of Law and Political Sciences of the University of Vienna, where he obtained the degree of Doctor of Laws in 1913. During the First World War he was called up to the Austrian army in 1915 and served in the Military General Governorship. In 1916 Łoś was moved to the District Headquarters in Olkusz, and then to the Civil Administration of the General Governorship in Lublin as that Administration’s secretary. He took an active part in the formation of Polish administration in the lands of the former Polish Kingdom. It was in that period that he met Józef Piłsudski. In 1918-1931 he was employed by the Ministry for Foreign Affairs. In 1920 he fought in the battle of Warsaw, the decisive event of the whole Polish-Soviet war. In the Foreign Ministry, he headed the Northern Office, and then the Office for International Systems. He dealt with the international aspects of Poland’s Ukrainian minority. He spoke in the assembly of the League of Nations and, in the mid-1920’s, he undertook to mediate concerning the quicker recognition of the independence of Polish Orthodox Church by the Ecumenical Patriarchate of Constantinople. In 1926-1929 he worked in London as a legal counsel of the Polish embassy. In 1931 he left the diplomatic service and settled down in Niemce estate (in the Lubartów District), where he dedicated himself to writing, his works joining the current of Polish-Ukrainian agreement. From 1932 he collaborated with “Biuletyn Polsko-Ukraiński”, and in the second half of the 1930’s he published in the organs of the Vilnius Conservatives, i.e., in “Bunt Młodych” and in “Polityka”. He also wrote for other Conservative papers, including “Dzień Polski”, “Nasza Przyszłość”, or “Przegląd Współczesny”, as well as for Ukrainian titles such as “Nowa Zoria” and “Meta”. He privately took up numerous efforts aimed at normalizing the Polish-Ukrainian relations and interchanged letters frequently with the leading Ukrainian figures from the field of politics and journalism. He headed diplomatic missions on behalf of the Polish Government; for instance, in 1938-1939 he successfully conducted negotiations regarding the conditions of Prime Minister Witos’ return to Poland from his forced emigration. Łoś also pursued social activity: in 1933-1939 he was a member of the Board of the Chamber of Agriculture in Lublin, and in 1931-1936 – the secretary of the Board of the Association of the Polish Knights of Malta. During the Second World War he stayed at the Niemce estate and took an active part in defending the local inhabitants against the German repressions. Following the capture of the Lublin Region by the Red Army, he was arrested by the functionaries of Polish Security Office (UB) on the 18th of October, 1944, and imprisoned at the Lublin Castle. He was released on the 7th of May, 1945, and began to work at the Catholic University of Lublin (KUL). He participated in the proceedings of the Scientific Councils of the Ministry for the Regained Territories, Ministry of Agriculture, and Ministry of the Reconstruction. In 1957 he became assistant professor, and two years later associate professor of the Catholic University of Lublin. In 1957-1959 he was the dean of the Faculty of Humanities at the KUL. In 1961 he retired but continued his scientific work till the end of his life. His major works include: Polityka Wielkiej Brytanii (under the pen-name of Andrzej Januszowski) published in ‘Przegląd Współczesny’, Nos. 78, 79, and 80 in 1928/1929; Sytuacja międzynarodowa a Ukraińcy Haliccy, in ‘Nasza Przyszłość’, vol. XXX; O konstruktywną politykę na Rusi Czerwonej (Warsaw, 1932); Problem polsko-ukraiński w ziemi czerwińskiej (co-authors: A. Bocheński and W. Bączkowski; Warsaw, 1938); Hellada na przełomie (Warsaw, 1938); Sprawa agrarna w Rzymie II-go i I- wieku przed Chrystusem (Lublin, 1946); Warunki bytowania ludności polskiej na Ziemiach Odzyskanych (Lublin, 1946); Sylwetki rzymskie (Warsaw, 1958); Rzym na rozdrożu. Studium monograficzne o Katonie Starszym (Warsaw, 1960), and Świat historyków starożytnych (Kraków, 1968).