Violent sectarian clashes erupt in Belfast between August 23 and August 31, 1920, during a period of intense political and social unrest in Ireland. At least 30 people are killed, and hundreds are injured. In the wake of the violence, large numbers of Catholic workers are expelled from the city’s shipyards and engineering firms, particularly Harland & Wolff, by loyalist mobs. These expulsions mark one of the most notorious episodes of anti-Catholic discrimination in Northern Ireland’s industrial history.