In late November 1867, events in Manchester, England, reverberated around the world, sparking public displays of Irish nationalism from Dublin to Philadelphia. Three Irish nationalists — William Allen, Michael Larkin, and Michael O'Brien — were executed by English authorities for the killing of police officer Charles Brett. The men belonged to a secret society known as the Irish Republican Brotherhood (also known as the Fenians), which had carried out a raid on a police caravan carrying two of the organization's leaders. In the process of freeing the prisoners, the band killed Brett.

Allen described his pending execution in a passionate letter to family members on Nov. 22: "I am dying an honorable death. I am dying for Ireland, dying for the land that gave me my birth, dying for the island of Saints, and dying for liberty." The following day, authorities publicly hanged Allen, along with Larkin and O'Brien, before thousands of onlookers.The three became known as the Manchester Martyrs.

Philadelphia's Fenians planned one of the largest North American demonstrations in response to the executions. Irish activists built coffins symbolizing Allen, Larkin, and O'Brien and marched through the city, arriving at Broad and Chestnut Streets to listen to the fiery oration of prominent lawyer John O'Byrne, who called for armed retribution.

The Fenians represented a grave threat to British rule of Ireland, in part because of their formidable international network. Irish Americans were particularly open to Fenian politics. In the 1840s, the Great Famine — during which one million Irish died from starvation and disease even while the British exported food from Ireland — had a profound impact on Irish opinion regarding British occupation, and also led to mass emigration to the United States. In U.S. cities, Irish immigrants confronted bigotry and nativist violence, which further contributed to Irish nationalist sentiment.

A group of Irish Americans organized the Fenian Brotherhood in 1858 as part of the revolutionary Fenian movement, providing financial and political support to their counterparts overseas.The Fenians were particularly active in Philadelphia, which had an Irish population of approximately 72,000 by the 1850s. (The city had also witnessed its share of nativist violence, evident in the anti-Irish riot of 1844, which shaped the politics of the city's Irish residents.)

Philadelphia's prominence in the Fenian movement during the 1850s and 1860s stemmed in part from the efforts of printer James Gibbons, who helped found the group's national body and helped bring the Fenians' first national convention to the city in 1863. In Philadelphia and in cities across the United States, Fenians contributed to recruitment efforts of former Union soldiers to travel back overseas and participate in the armed struggle against the British. They also supported nonviolent activities, funding protests and contributing to relief funds abroad.

The Brotherhood's revolutionary zeal and predilection for armed violence caused debate within the Catholic Church, which played a central role in the religious and social lives of Irish Americans. Many leading Catholics in Philadelphia, including Archbishop James Wood, denounced the Fenians. On St. Patrick's Day in 1868, the Philadelphia-based Catholic Herald declared that "nothing but trouble and misery has been created both in America and Ireland" by the Fenian movement. Some rank-and-file priests, however, sympathized with the nationalist cause, including Father Patrick Moriarty, pastor of St. Augustine's Church at Fourth and Vine Streets.

Defying Archbishop Wood's directive for clergy to forsake Fenian politics, Moriarty delivered a rousing speech at an organizing event at the Academy of Music in 1864 during which he called Britain a "tyrant, robber, [and] murderer" and justified armed resistance to the British government. Gibbons printed the speech at his Chestnut Street press.

Due to internecine conflicts, the Fenian Brotherhood lost influence throughout the 1870s and disbanded in 1880. Clan na Gael — another Irish American group — emerged from the collapse of the Fenian Brotherhood, and existed into the 20th century. It became the largest organizational funder of the Easter Uprising in 1916 and the Irish War for Independence.

Patrick Glennon is a communications officer at the Historical Society of Pennsylvania.