Joseph Mary Plunkett (1887-1916) was born at 42 Upper Mount Street, Dublin, the son of George Noble Plunkett, a papal count and his wife Josephine Cranny. He was educated by the Jesuits at the Catholic University School, Belvedere College and Stonyhurst College in Lancashire, where he wrote his first poetry and became interested in mystics such as St John of the Cross and St Teresa of Avila. He contracted tuberculosis as a young man and spent periods in Italy, Algeria and Egypt in the years 1910-12.

Plunkett met Thomas MacDonagh when he had him as a tutor in Irish in preparation for the University College, Dublin matriculation examinations. MacDonagh was to become a close friend, as both were interested in poetry, religion and mysticism. When MacDonagh established the literary journal Irish Review in 1911, he published some of Plunkett’s early poems. MacDonagh also edited Plunkett’s first collection of poems, The Circle and the Sword (1911). Together with Edward Martyn, they were both involved in setting up the Irish Theatre in Hardwicke Street in November 1914.

Plunkett maintained an interest in the Irish Review, taking it over and becoming editor when it had financial difficulties in 1913. Under his direction the journal became increasingly political, supporting Arthur Griffith’s Sinn Féin policies and the workers’ stand during the 1913 lock-out. Elected to the provisional committee of the Irish Volunteers on their foundation in November 1913, he promoted the new organisation in the Irish Review, his intemperate language resulting in the seizure of copies under the Defence of the Realm Act.

By now a member of the Irish Republican Brotherhood and committed to revolution by force of arms, in April 1915 Plunkett went to Germany to assist Sir Roger Casement in procuring arms and assistance. In May he was appointed to the IRB Military Council, mainly because of his key position as director of military operations in the Irish Volunteers. Together with James Connolly and Séan Mac Diarmada, he was heavily involved in the final preparations for the Rising, especially in the planning of military strategy for which he displayed considerable talent. He and MacDiarmada are believed to have forged a document released on 19 April 1916, supposedly emanating from Dublin Castle, which suggested that the authorities were about to suppress the Irish Volunteers. The intention presumably was to stiffen the resolve of Eoin MacNeill and the general body of Volunteers; the status of the document has never been determined.

In very poor health and recovering from a major operation on glands in his neck, Plunkett nevertheless joined other members of the Provisional Government in the General Post Office. Following the surrender, he was tried by court-martial and sentenced to death by firing squad. He was engaged to be married to Grace Gifford, a sister-in-law of Thomas MacDonagh; the authorities allowed them to marry in Kilmainham Jail on the night before his execution on 4 May.