The Irish Football Association (IFA) was founded in Belfast in 1880. It was the governing body for soccer for the whole of the island of Ireland. Soccer in Ireland was united for over forty years. It was, though, an uneasy alliance. Divisions in the sport reached a climax after the First World War, culminating in the split of 1921.

A look at the 1921 split of soccer in Ireland between North and South, through primary sources from the Irish Football Association, Football Association of Ireland (FAI), the English Football Association, and the Leinster Football Association as well as contemporary newspaper sources. It details the events and causes that led to the split and compares soccer to other sports that remained or became united after the island's partition. It recounts the early years of the FAI and its attempts to gain international recognition. Many efforts were made to heal the division throughout the years. Some came very close, all ultimately failed, leaving soccer in Ireland today, as it is politically, divided North and South.