The violence that took place in Belfast between 1920 and 1922 was unique in revolutionary Ireland. Peter Hart has described the conflict there as ‘a communal war and a sectarian war, fought on the basis of ethnic mobilisation rather than paramilitary organisation’. Violence comprised rioting, sniping, bombing, burning, reprisal killing, and forced expulsion. Belfast followed its own revolutionary timeline and, in A. C. Hepburn's words, ‘appeared to be one of the most peaceful places in Ireland’ until it witnessed a wave of rioting in July 1920 that coincided with the removal of thousands of Catholic workers from the city's shipyards. The following two years saw peaks of violence, usually around the traditional Orange celebrations in July, followed by periods of relative peace and culminating in the most intense period of violence during the first six months of 1922. In this regard, the violence formed part of a longer tradition of ethnic rioting and communal disturbances dating back to the 1850s and continuing to the present day. As intense as it was, there was little that was new about violence in Belfast at this time.

A label commonly used, then and since, to describe the violence that occurred in Belfast (and similarly in Lisburn) against Catholics between 1920 and 1922 is ‘pogrom’ and Tim Wilson has referred to a ‘competition in murder’ whereby rival communities used violence aimed at inflicting enough suffering to bring about defeat for the opposition. Though Catholics were disproportionate victims of violence, both sides of the religious divide perpetrated violence against the rival community ranging from intimidation and expulsion to killing.

Estimates of fatalities from two years of violence have varied from 409 to 498. Eunan O'Halpin and Daithi Ó Corráin have counted 225 deaths as a result of political violence between January 1919 and December 1921. In addition, up to 2,000 serious injuries were inflicted. Robert Lynch has recorded 650 homes burned, 8,000 civilians forced from their homes, and 6,000 from their jobs in 1920 alone, while estimates for evictions and workplace expulsions for the full two years are as high as 23,000 and 10,000 respectively. It is often impossible, though, to identify the perpetrators of lethal violence in Belfast and non-lethal activity is even more difficult to track.