Even before independence
Belfast Riots in July 1920

The immediate causes were the shooting of Smyth in Cork (he was from Banbridge) and the tensions arising from the 12th July (fanned by Carson). The more long term causes were fears about jobs by Protestant workers. Parkinson notes that unemployment was 26% in Belfast at this time after post-war depression. Protestant workers felt they were taking their 'own' jobs back.

Parkinson says there was about 93,000 Catholic workers in the city at this time (Parkinson (2004), pgs 33-35) and he estimates that around 10,000 workers expelled including several hundred female textile workers. He says that most of the expulsions occurred within the first few days but some intimidation did occur into the following month and even into early September when Catholic workers would be forced out of work for refusing to sign 'loyalty' documents. Also, included were about 1,800 Protestant trade unionists and socialists who were also expelled from their work – the latter were called 'rotten Prods' by the unionist leadership (Parkinson (2004), pgs 35-36 & 328). Parkinson further estimates that over the period of the conflict in Belfast (i.e. up to summer 1922), over 20,000 Catholics were displaced (Parkinson (2004), pg 62).

Parkinson also says that there is little evidence that Unionist Party had organised expulsion but that the Unionist leaders failed to condemn them. Carson was later to express his 'pride' in the actions of his shipyard 'friends' (Parkinson (2004), pg 31). He goes onto say "members of the BPA and other loyalist splinter groups undoubtedly benefited from easy access to their considerable arsenal and were certainly responsible for the initial industrial expulsions and several sectarian murders. Although the unionist establishment may not have co-ordinated the campaign of violence, it is undeniable that the Belfast authorities had been bracing themselves for an outbreak of communal disturbances during the summer of 1920." (Parkinson (2004), pg 309) He goes on to say that the more incisive deployment of troops in Belfast would have probably reduced the level of violence. McDermott says that "There is no significant evidence that the unionist leadership ordered the expulsions from the shipyards … but … the expulsions mark the beginning of what … the whole of the nationalist community called the 'pogroms'." (McDermott (2001), pg 33)
The response by a number of prominent nationalists and republicans in the North in August (including Sean McEntee; Denis McCullough; Bishop McRory and Rev John Hassan) is to set a 'Belfast Boycott Committee' which aims to force Belfast businesses to take back expelled Catholic workers by pushing a vigorous boycott of all goods produced in Belfast. They have success with county councils in the South and, while initially reluctant, the Dáil takes responsibility for it from January 1921.
http://www.dcu.ie/~foxs/irhist/july_1920.htm

21-24 Jul
Quote:
Major riots in Belfast. On the morning of the 21st July, members of Belfast Protestant Association put up posters on gates of Queen's Island calling for meeting of 'all Unionist and Protestant workers' at lunchtime. Nearly 5,000 meet and afterwards go on rampage attacking Catholic workers. Clothes are torn of potential victims to see if they are wearing any Catholic emblems. Some try to escape by swimming the Musgrave Channel but are pelted by nuts, bolts, rivets, etc (called 'Belfast confetti'). Most Catholics and socialists are removed from yards by afternoon. At least 20 men have to receive hospital treatment. After the expulsions from the shipyards, Catholic workers are ejected from other industrial sites in the city including Sirocco Works, Musgraves, Combe Barbours, Mackies Foundary and several linen mills.

In the ensuing three days of riots 13 people were killed (says Hopkinson but Macardle says 17; Phoenix says 18 and McDermott says 18 made up of 10 Catholics and 8 Protestants. Parkinson names 21 people as being killed – 11 of whom would seem to have been Protestant. During these riots, hundreds of (mostly Catholic) families are driven from their homes. There was also the destruction of businesses and houses belonging to Catholics in Bangor, Banbridge, Dromore and other small towns
21 July 1920
In Belfast, 'Protestant and unionist' workers from Workman Clark's shipyard marched into Harland and Wolff's yard and forcibly expelled all Catholic and socialist workers. Some were forced to swim for their lives. In three days of violence seven Catholics and six Protestants were killed in the city.
Jim Carroll