There is no history or evidence to support the claim that the Provisional IRA has prevented serious loyalist violence against Catholics in Northern Ireland.
This claim is being held out by republicans as one of the main reasons the IRA cannot hand over or destroy its weapons.
Even the structure of the Provisional IRA does not sit easily with the role of a defensive organisation designed to stop attacks on Catholics or even incursions into nationalist areas.
The IRA's military structure has been refined to a cell-structured organisation, with only a few hundred people likely to have access to guns at any one time. Most of its organisation is given over to raising funds and storing weapons for the small fighting machine responsible for bombings and assassinations.
Its arsenal is also not suitable for a defensive role in nationalist areas. It has perhaps 1,000 assault rifles, but these would be inadequate for protection on a large scale.
Most of its stockpile of weapons consists of bomb parts, mortars, home-made grenades and explosives. It is known to have only a few medium machineguns, the type of infantry weapon most suitable for defending territory.
Among the arguments against decommissioning put forward by republicans is that the Catholic community needs defending against future possible aggression from heavily armed loyalists.
In support of this contention it is pointed out that there are about 140,000 legally held firearms in Northern Ireland, and most of these are held by the Protestant majority community. Added to these legally held weapons are those held illegally by the loyalist terrorist organisations.
In fact, there has always been a high number of firearms held both legally and illegally in Northern Ireland, and it is probable that the quantities held by both sides have remained constant since Partition.
The possession of a republican arsenal has never prevented periodic outbreaks of sectarian violence since the 1920s. It had no impact on preventing the widespread intimidation and sectarian violence that characterised the main period of communal violence from 1969.
Most of the 800 loyalist assassinations of Catholic civilians in Northern Ireland have been in areas where Catholics lived in mainly Protestant areas or on the periphery of nationalist areas in Northern Ireland.
The loyalist violence against Catholics, in areas such as south-east Antrim, north Belfast, south and east Belfast, north Armagh and north Down, could be described as ethnic "cleansing" of these areas. Over the 30 years of the troubles tens of thousands of Catholics were forced out of their homes in this low-level pogrom.
Significant but smaller numbers of Protestants were forced out of their homes in predominantly Catholic areas.
The view that the Provisional IRA prevented attacks on Catholics through "defence" of nationalist areas from loyalist attack cannot be fully supported by events or analysis of the violence in the North.
The IRA devoted almost its entire efforts to a covert war against police and the British army in the North.
It killed only a small number of loyalists, less than 30, according to a detailed book on the North's killings, Lost Lives.
In all, the IRA killed some 1,800 people but failed to prevent loyalists from killing 800 Catholic civilians. The IRA itself also killed some 400 Catholics and a similar number of Protestant civilians.
In its crudest form in the 1970s, the IRA's approach to "defending" the Catholic community from loyalist attack took the form of attacks on Protestant civilian targets.
The worst instance of this was the "Kingsmill Massacre" in January 1976 when the IRA stopped a bus carrying Protestant mill workers, lined them up against a ditch and shot dead 10 men.
About 25 IRA members from south Armagh carried out this atrocity, which was designed to stop loyalists from killing Catholic civilians in the area. Loyalist attacks in the area did fall off soon afterwards, leading many republicans to claim that the Whitecross massacre had been effective.
However, the decrease in loyalist violence was because the RUC had rounded up large numbers of UVF members from the mid-Ulster area and imprisoned them.
Much of the Provisional IRA violence of the early and mid-1970s was part of the "tit-for-tat" cycle of retaliation and counter-retaliation.
In the first years of the Troubles the Provisional IRA and the UVF engaged in a war of attacks on pubs and other targets in each other's "territory". After the worst of these bombings, when 15 Catholics were killed by a UVF bomb at McGurk's Bar in north Belfast, the IRA retaliated with a no-warning bomb outside Moffat's furniture store on the Shankill Road, killing two adults and two infants.
The last round of this type of sectarian violence occurred in October and November 1993, when the IRA killed nine Protestants on the Shankill Road in a bomb attack on the UDA's offices situated above Frizzell's fish shop.
The bombing of Frizzell's was the culmination of a series of tit-for-tat sectarian killings between the then young IRA leader in north Belfast and his UDA counterpart on the Shankill Road.
After Frizzell's the UDA killed about 26 Catholics in retaliation. Again, this round of loyalist violence ended only when the RUC rounded up the UDA gunmen who killed seven people in a Catholic-owned pub in Greysteel, Co Derry.