Final answer:
The Irish Republican Army (IRA) is the group most associated with revolutionary nationalism in Ireland, having been a key player in the Irish War of Independence and the Easter Rising. Sinn Féin also played a significant political role in the pursuit of an independent Ireland.
Step-by-step explanation:
Groups Associated with Revolutionary Nationalism in Ireland
The group most associated with revolutionary nationalism in Ireland is the Irish Republican Army (IRA). This group was directly involved in actions against British rule, notably during the Irish War of Independence and the Easter Rising of 1916. Sinn Féin, initially a political party fighting for Irish independence, has often been associated with the IRA and participated in the political process to achieve an independent Ireland. Sinn Féin's aim differed in method, advocating political means where sometimes the IRA adopted more violent measures. The other groups mentioned, such as Fianna Fáil and the Ulster Volunteer Force, are related to the politics and conflicts of Ireland but are not primarily associated with revolutionary nationalism in the same way as the IRA.
After years of conflict, including the Easter Rising and later the war of independence, the south formed the Irish Free State while the north remained part of the UK. Despite the establishment of the Free State and later the Republic of Ireland, some nationalists, particularly within the IRA, continued to seek the unification of Ireland and complete independence from British influence.