McCullagh was born in Dungannon, Northern Ireland, in 1874. He began his journalism career as a staff reporter at the Glasgow Observer (later Scottish Catholic Observer), and would continue writing for the newspaper through 1906-1937. From 1898, he was a correspondent for the New York Herald. In 1903, he was living in Japan, working for the English-language newspaper The Japan Times. Observing the growing tension between the Empire of Japan and the Russian Empire, he studied the Russian language. In 1904, he moved to Port Arthur, the major Russian military base in Manchuria, obtaining a post as a correspondent for the Novi Kraï (New Land) newspaper of Port Arthur. At the start of the Russo-Japanese War, he became a non-military observer embedded within the Imperial Russian Army. In March 1905, he was evacuated as a prisoner of war, traveling from Dalny to Ujina on the Nippon Yusen liner Awa Maru. His experiences were published in 1906 as With the Cossacks: Being the Story of an Irishman Who Rode With the Cossacks Throughout the Russo-Japanese War.
McCullagh died in White Plains, New York in 1956.
- "Has the War Correspondent Seen His Last Fight?," Review of Reviews and World's Work, Vol. XLVII, 1913.
- Coffey, Jim (19 April 1985). "Writer of the War" (4097). Scottish Catholic Observer.
- McCullagh, Francis. (1906). With the Cossacks, pp. 3-4., p. 3, at Google Books
- McCullagh, 1906: pp. 372-386.
- "Journalists in Franco's Spain," Catholic Herald, 22 October 1937.
- (1906). With the Cossacks; Being the Story of an Irishman who Rode with the Cossacks Throughout the Russo-Japanese War. London: Eveleigh Nash. OCLC 777525 [Reprinted by Naval and Military Press, 2009].
- (1910). The Fall of Abdul-Hamid, Methuen & Co., Ltd.
- (1912). Italy's War for a Desert, Being Some Experiences of a War-Correspondent with the Italians in Tripoli. London, Herbert and Daniel.
- (1921). A Prisoner of the Reds, the Story of a British Officer Captured in Siberia. London. John Murray.
- (1924). The Bolshevik Persecution of Christianity. New York, E. P. Dutton [1st Pub. London, John Murray, 1924].
- (1928). Red Mexico; A Reign of Terror in America. New York, L. Carrier & Co.
- (1937). In Franco's Spain: Being the Experiences of an Irish War Correspondent During the Great Civil War. London, Burns, Oates & Washbourne, Ltd.
- Horgan, John (2009). "Journalism, Catholicism and Anti-Communism in an Era of Revolution: Francis McCullagh, War Correspondent, 1874-1956," Studies: An Irish Quarterly Review, Vol. 98, No. 390, pp. 169–184.
- McNamara, Patrick J. (2006). "Russia, Rome, and Recognition: American Catholics and Anticommunism in the 1920s," U.S. Catholic Historian, Vol. 24, No. 2, pp. 71–88.