Raised through public appeal, newspaper and television advertisements,[1] their official role was the "defence of life or property in Northern Ireland against armed attack or sabotage" but unlike troops from Great Britain they were never used for "crowd control or riot duties in cities".

[7][8][9][10] The regiment was originally intended to more accurately reflect the demographics of Northern Ireland, and began with Catholic recruits accounting for 18% of its soldiers; but by the end of 1972, after the introduction of internment this had dropped to around 3%.

After discussions, they advocated a strength of 6,000 men (2,000 more than the Hunt recommendations), combat dress for duties, a dark green parade uniform, county shoulder titles, and a "red hand of Ulster" cap badge.

For the British government's part, those defending the proposed name argued that the term "Ulster" should still be included because of precedent; in the past, it had been attached to certain regiments in Northern Ireland.

Vetting was carried out by a Regular Army team of mostly retired officers from outside Northern Ireland including a vice admiral and a number of major generals.

[55] This was partially explained by the fact that in the mostly Catholic town of Newry, the Territorial Army company of the Royal Irish Fusiliers had been disbanded in 1968 and the vast majority of its soldiers had joined the UDR en masse.

[61] However, some of these men were already past retirement age and after their year's contract was up they were replaced by lieutenant colonels from the regular army, the first of these being Lt Col Dion Beard of the 1st Royal Tank Regiment (1 RTR) who took over at 3 UDR on 15 February 1971.

Camouflage jackets were worn and headgear was a distinctive dark green beret with a gold coloured "Maid of Erin" style harp, surmounted by St Edward's Crown (in later years this was dulled down by blackening, a common practice for units of the British army when wearing cap badges on operational duties).

[79] Several battalions were supplied with rigid Dell Quay Dory craft for patrolling waterways shared with the Republic of Ireland in an attempt to prevent gun-running across these narrow channels such as Carlingford Lough.

The shore-based dories proved inadequate and a paper was submitted by 3 UDR in 1972,[citation needed] recommending a naval vessel to be stationed in the centre of Carlingford Lough[80] to assist with the suppression of gun-running.

[84] Over time these were replaced with Stornophones[85] as vehicle sets with preselected frequencies which operated on the NINET rebroadcast system, working through masts strategically placed on various high points throughout Northern Ireland such as Slieve Croob.

[88] This content of this information card was seen as vitally important and all soldiers were taught to be entirely familiar with it as it contained specific instructions to be followed when opening fire on a suspected enemy.

Writing in 1991, Ken Maginnis recounted that the Regiment had originally been formed as a "sop to Unionism" and it was never intended to have a "serious" operational role, with UDR soldiers at first being assigned to "demeaning" and pointless posts such as guarding water reservoirs.

By 1980, the full-time element had matched the numbers of part-timers and the regiment's role had expanded to include tactical responsibility for 85% of Northern Ireland, supporting the Royal Ulster Constabulary.

[162][103] The last was part-time Private William Megrath of 11 UDR who was shot dead in July 1987 as he drove through the Twinbrook area of west Belfast on his way home from his civilian job.

[169][170] This changed when on 29 November 1972, the GOCNI, on instructions from Westminster,[171] announced that dual membership of UDR and paramilitary organisations would not be tolerated and began a purge which saw 171 soldiers with links to the UDA discharged by the end of 1975.

[177] An August 1973 draft document prepared by British military intelligence asserted that the "vast majority" of UDR weapons stolen up to that point were in the possession of loyalist paramilitaries.

According to Lethal Allies: British Collusion in Ireland, by Anne Cadwallader, permutations of the group killed about 120 people – almost all of whom were Catholic civilians with no links to Irish republican paramilitaries.

In January 1976, Davis and another UDR soldier, Ronald Nelson, went to Millar's Londonderry farm to persuade him not to give evidence against them in a case arising from the earlier armed robbery of £1,400 from a post office.

Nelson was also convicted, with others, for his part in additional sectarian crimes including possessing firearms, car theft, armed robbery, arson and a petrol bomb attack on as Catholic-owned draper's shop which caused £162,000 worth of damage.

[209] Seven serving UDR soldiers of the Ballymena platoon were convicted of a range of terrorist offences in 1987,[209] including involvement in the murder of a Catholic man by "Shankill Butcher" Lennie Murphy in September 1982.

[211] In 1984 an arms haul of twenty-eight firearms that included several rifles, revolvers, and home-made submachineguns as well as 5,000 rounds of ammunition was uncovered on the County Antrim farm of a serving UDR soldier.

Michael Taggart and UDA member Jackie Courtney used the taxi service to facilitate the theft of intelligence documents on republican suspects from Girdwood Barracks in North Belfast by a UDR soldier, Joanne Garvin.

[213] In October 1986, four Catholic families, living in a housing estate in Ballymena, County Antrim, received threatening letters from the UDA, containing bullets, giving them a week to leave their homes.

Another arms cache including an RPG-7 launcher with warheads, assault rifles, hand grenades, and 4,900 rounds of ammunition, also linked to Ulster Resistance, was found at the home of a UDR soldier in Richill, County Armagh.

[227] In December 1991, three serving UDR soldiers and a close associate were arrested and questioned for several days about the murder of four men in a gun attack by the UVF in Cappagh, County Tyrone in March 1991 before being released without charge.

[228] A Historical Enquiries Team (HET) report released by the Police Service of Northern Ireland (PSNI) claimed the UDR men "were also named as responsible for other murders".

This was suggested to be partially due to increased security and also that "the reduced credibility of Protestant extremist groups in the eyes of the majority community, has made the subversion of UDR members more difficult.

[245] After the Hillsborough Agreement the Democratic Unionist Party (DUP) began a campaign with the apparent motive of reducing morale in the regiment and causing mass resignations by undermining the confidence of soldiers in their officers.

[278] The City of Belfast and a number of boroughs throughout Northern Ireland paid their own tribute to the regiment by granting freedoms including: North Down, Larne, and Newtownards.