The remaining IRA weaponry is understood to be sufficient to arm up to 1,000 members of the organisation, writes Gerry Moriarty, Northern Editor
Gen John de Chastelain's decommissioning body is today expected to announce that the IRA has carried out a third and substantial act of decommissioning as part of a deal leading to elections and a restored Assembly and Executive.
It is estimated that it has a huge arsenal of well over 100 tons.
One of the final stumbling blocks at yesterday's negotiations was the issue of disarmament and how further decommissioning would be accepted by unionists as being real and substantial.
Sinn Féin has acknowledged that because there was such little detail about the last two acts of decommissioning that unionists will be sceptical about any third act that would only involve the IRA and Gen John de Chastelain's decommissioning body.
In these negotiations Sinn Féin has continued to insist to the British and Irish governments and the Ulster Unionists that IRA decommissioning must remain an issue solely between the IRA and the Independent Commission on Decommissioning.
Ulster unionists, it is understood, had proposed that an independent person whom they trusted would be invited to view and verify a third decommissioning event, but that this was rejected by Sinn Féin.
At the IRA's insistence no detail was given about the IRA's first act of decommissioning in October 2001.
When the IRA further disarmed in April 2002 the only indication of the extent of the decommissioning was a statement from Gen de Chastelain that it was "substantial".
A possible compromise this time that might give some assurance to unionists is that Gen de Chastelain, with the agreement of the IRA, provides a detailed inventory of what arms and explosives are rendered unusable.
Because of the lack of detail about the last disarmament events it is unclear what the extent of the IRA's remaining arsenal is, although it is understood to be substantial - probably sufficient to arm a force of about 1,000 IRA members.
The arsenal is said to include up to 1,000 Kalashnikov rifles, about 500 handguns, 50 heavy and general-purpose machine-guns, RPG-7 rocket launchers, home-made grenade launchers and mortars, as well as a significant amount of Semtex, possibly two tons or more.
Such is the professional nature of the IRA that these arms and explosives are understood to be carefully stored, and that there is little chance of them becoming unusable through decaying in the ground.
Most of the IRA's arsenal came from Libya, through its leader Col Muammar Gadafy. The IRA built up contacts with Col Gadafy in the early 1970s and it is understood that the first two shipments containing an estimated 500 rifles, 500 pistols, 40,000 rounds of ammunition, and explosives arrived in 1972. The MV Claudia, carrying a third shipment, was intercepted off Helvick Head, Co Waterford, the following year.
There were further shipments from Libya between 1977 and 1978 containing RPG-7 rocket launchers, rifles, handguns and explosives. Most of the IRA's arsenal arrived in Ireland from Libya between 1985 and 1987.
It is understood that three or four huge shipments got through to Ireland over this period. The extent of the gun-running came to light by accident when the ship, the Eksund, was arrested in the Bay of Biscay in October 1987 by French customs checking for drug smuggling.
On board were found 150 tons of weapons including 1,000 AK47 rifles, 10 anti-aircraft machine-guns, one million rounds of ammunition and one million mortar shells. Sources said the ships that got through would have carried about 135 tons of weapons and explosives.
With such a huge arsenal the IRA then started improving its bomb-making capability, smuggling in electrical components for bombs from Europe and the US. Its ability to make sophisticated home-made bombs, including increasingly effective mortars, developed through the 1980s and early 1990s.
In 1984 British, Irish and US intelligence services had a notable success when the Marita Ann trawler was arrested off the Kerry coast carrying seven tons of arms, which originated from a crime gang in Boston.
Current Kerry Sinn Féin TD Mr Martin Ferris was sentenced to 10 years for his part in that gun-running operation.
The IRA also imported from the US a number of Barrett Light Fifty sniper rifles, which they used to kill nine British soldiers and police officers in south Armagh. The IRA boasted about these killings with "Sniper at Work" mock road signs in south Armagh. The IRA still has a number of these rifles and may have acquired more after its ceasefires in the 1990s.
In the late 1990s the IRA smuggled in about 200 handguns and sub-machineguns from Florida, sending them through the postal system.
Some of these weapons were used by the IRA to kill alleged drug dealers, although the IRA did not admit to the murders.