The attack on Derryard checkpoint was a large guerrilla assault carried out on 13 December 1989 by a Provisional Irish Republican Army (IRA) unit against a British Army permanent vehicle checkpoint manned by soldiers of the King's Own Scottish Borderers (KOSB). It occurred near the Northern Ireland-Republic of Ireland border at Derryard (near Rosslea), County Fermanagh. The IRA team withdrew after the rapid reaction of a British Army patrol. A large van bomb left by the attackers also failed to detonate. The action left two British Army soldiers dead and one badly wounded.
According to journalist Ed Moloney, the IRA Army Council, suspecting a large degree of penetration by informers at the grassroots level of the organisation, decided to form an experimental flying column instead of the usual active service unit in order to mount a large scale operation against a permanent vehicle checkpoint along the border. The idea was to find an effective way to prevent any leak which could result in another fiasco like the Loughgall ambush in 1987.
Moloney maintains that the planning was in the charge of Thomas Murphy, alleged leader of the South Armagh Brigade, and was to be conducted by East Tyrone Brigade member Michael "Pete" Ryan. The column was made up of volunteers from throughout Northern Ireland. Journalist Ian Bruce, instead, claims that an Irishman who served on the Parachute Regiment was the leader of the IRA unit, citing intelligence sources. The unit would be composed of around 20 volunteers, but the action properly was to be the responsibility of 11 volunteers.
The assault would involve the use of two 12.7mm DShK machine guns, 11 AK-47s, different kinds of grenades, and a flamethrower. The bulk of the flying column would be driven to the checkpoint on a makeshift armoured truck. To assure widespread destruction, the column decided to detonate a van bomb after the initial surprise assault. The chosen target, a vehicle checkpoint at Derryard, near Rosslea, was manned by 8 soldiers of the 1st Battalion of the King's Own Scottish Borderers regiment and a member of the RUC.
After launching a number of grenades (either RPGs or home made devices), the IRA volunteers managed to break into the compound using the armour-plated lorry, supported by automatic fire and the flamethrower's stream of fire. In the process they killed two soldiers, Pte James Houston and L/Cpl Michael Patterson. Cpl Law was severely wounded by shrapnel and later airlifted for treatment. The defenders were forced to seek shelter in sangars, from where they fired into their own base. The IRA unit left inside the complex a van loaded with 400-lb (182 kg) of Semtex, which failed to explode. The attack was finally repulsed by a Borderers section from the checkpoint that was patrolling nearby, with the support of a Wessex helicopter. The patrol fired more than 100 rounds. The IRA column, at risk of being surrounded, then fled in the truck, possibly toward the border.
There was outrage in Parliamentary and Unionist circles. A supposedly well-defended army border post had been overrun by the IRA and two soldiers killed. On the other hand, there was also some disappointment among Republicans. Indeed, despite the positive propaganda effect, the quick and strong reaction from the British Army troops convinced some top level members that the Army council was infiltrated by a mole.
A senior British Military officer, when quizzed about the IRA attack said:
They are murdering bastards, but they are not cowards. This team actually pressed home a ground attack right into the heart of the compound. That takes guts when there are people firing back.
KOSB officers and security sources correctly concluded that the IRA unit involved was not locally recruited, putting the blame instead on IRA members from Clogher, County Tyrone and South Monaghan, in the Republic.
Two British soldiers, Corporal Robert Duncan and Lance Corporal Ian Harvey both received the Distinguished Conduct Medal (DCM), whilst L/Corporal Patterson received a posthumous Mention In Dispatches for his actions during the attack. The checkpoint was eventually dismantled in 1991.