Millen, Francis Frederick (1831–89), soldier, Fenian, and spy, was born in Co. Tyrone into a fairly prosperous catholic family. Little is known of his background except that he received a good education, considered himself a member of the gentlemanly classes and, aged 19, enlisted in the British army and may have served in the Crimean war (1854–6). He then moved to America, and about 1858 enlisted in the Mexican liberal army, a revolutionary force intent on overthrowing the existing clericalist regime and proclaiming a republic. He claimed to have been made lieutenant-colonel in 1858 and brigadier-general in 1861, but this was disputed by other sources. He left the army c.1861 and then seems to have worked for the US government in a semi-official capacity as an undercover agent or spy. After serving briefly with a revolutionary army in Guatemala, he rejoined the Mexican army, leading troops against the expeditionary forces of Napoleon III during the siege of Puebla (March 1863). After the proclamation of the Austrian Archduke Maximilian as emperor of Mexico (11 June 1864) he escaped to the US, allegedly with American help.
Millen had been in contact with the Fenian Brotherhood in America since 1860, when he had read about the affiliated Friends of Ireland Club in the San Francisco Times and expressed an interest in joining. In October 1864 he presented himself to the head of the Fenian Brotherhood, John O'Mahony (qv), in New York, and with the ending of the American civil war in April 1865 was dispatched to Ireland along with other Irish-American civil war veterans to help put the IRB on a military footing. O'Mahony told him to present himself to John O'Leary (qv) and James Stephens (qv), who made him president of the military council above more experienced officers. This caused resentment among American Fenians who had been officers in the US army and saw Millen as an inexperienced, theatrical, ‘banana-republic’-style officer.
Millen himself was unimpressed by the IRB, since its leaders were not soldiers. However, like the other American Fenian agents, he advised mounting a rising immediately. After the arrest of Stephens in November 1865, Millen, by virtue of his military rank, was named provisional head of the IRB, amid much opposition. Within hours of this appointment, Stephens smuggled out of prison a pencilled note ordering Millen to return to America. Millen protested, but his colleagues supported Stephens; a story was circulated that Millen had intended to abscond with funds, and he was further distrusted because he had flirted with a woman engaged to the imprisoned Fenian Denis Dowling Mulcahy (qv). Stephens escaped from prison on 24 November 1865, and Millen set sail for America a week later. He soon after resigned from the Fenian Brotherhood after O'Mahony had read a letter from Stephens denouncing him.
On 10 March 1866 Millen contacted the British consulate in New York and shortly thereafter provided a comprehensive and systematic report on the personnel of the Fenian Brotherhood in America, including the addresses and aliases of Irish-American agents and IRB activists in Dublin. He offered to do anything to achieve the re-arrest of Stephens, against whom he nourished a particular animosity. By May 1866 he had married and moved to Austin, Texas; there he wrote a lengthy account for Dublin Castle on the Fenians’ activities, for which he received £250. During 1867 Millen managed to restore his reputation in the faction-ridden and increasingly moribund Fenian Brotherhood and served intermittently as one of its leaders over the next eight years; it is unclear whether he remained in active British service during this time.
In 1872 he became a war correspondent for the New York Herald, a paper for which he continued to work until his death, and for which a fellow informant, an English journalist, Chester Ives, and several members of Clan na Gael also worked. As a war correspondent he was able to maintain some of his old military associations with the leaders of several South American states, and during 1876 served again briefly as an officer of the army of the Guatemalan Republic under Justo Rufino Barrios.
About 1876 he was appointed to the military board of Clan na Gael and three years later was sent to Ireland by the Clan leader, William Carroll (qv), to perform a military inspection of the IRB. On arrival he suggested being made an honorary member of the supreme council, but the council rejected his services, and he was sent back to America. In June 1880, to his chagrin, he was demoted from the Clan's military board and thereafter, together with Chester Ives, he began working for the British consul in New York in counteracting the extreme, small breakaway group from the Clan, the ‘United Irishmen of America’, which was in favour of making terrorist attacks on London. Although all members of this faction (which was soon infiltrated by British agents provocateurs) were expelled from the Clan, Millen formed during 1881 a secret organisation within the Clan. Although several Clan leaders distrusted Millen as an unprincipled adventurer, his capacity for mischief was enhanced by the election of a close associate, Michael Boland, as an autocratic Clan chairman in October 1882.
After the split in the Clan and the termination of its alliance with the IRB (August 1884), Millen was appointed a Clan leader by Boland, who ordered him to expel all camps opposed to the ‘dynamite war’, which he promptly did. In April 1885 Millen offered his services to E. G. Jenkinson (qv), assistant under-secretary for police and crime at Dublin Castle, and was promised £2,500 if he could help the government convict IRB leaders in Ireland. Hitherto his only coup had occurred in January 1881, when he had managed to attend a meeting of the supreme council in Paris and informed British intelligence of the names of the IRB leadership. In Paris he had also assisted Chester Ives and Richard Pigott (qv) in forging letters intimating the support of C. S. Parnell (qv) for the Phoenix Park murders. In order to substantiate the ‘Parnellism and crime’ propaganda campaign launched by The Times in March 1887, Millen, together with other agents provocateurs planned a bogus plot to disrupt Queen Victoria's forthcoming jubilee celebrations with bombings in London. However, the ‘jubilee plot’ resulted in the arrest of only four insignificant conspirators in November 1887 and had little propagandist affect. It created widespread suspicions about Millen in the Clan, and the British government dropped his services in the summer of 1888.
Millen was described as 5 ft 10 in. (1.78 m) in height, red-haired, and bearded, with a rather red face and a quiet slow manner of speaking. He died 10 April 1889 at his New York residence, 437 West Fifty-Seventh St., probably of natural causes, and was survived by his second wife and two daughters from his first marriage. A member of the New York Press Club and US Republican party, he had a reputation in New York as a sterling patriot. Trophies of his South American military career were displayed at his funeral, which was attended by some Fenian Brotherhood associates, who never suspected his duplicity. Probably through former agents of Jenkinson who were now Parnellites, Michael Davitt (qv) was able to learn of Millen's role as a spy. On 4 March 1890 Tim Harrington (qv) unsuccessfully attempted to raise the issue in the house of commons. The matter was not raised again until September 1911, after Sir Robert Anderson (qv) wrote to Blackwood's Magazine recalling the government's use of Millen during the Times commission.