Ballykinler Army barracks is to be without its own regiment for the first time since the Napoleonic wars 200 years ago.
Soldiers from 2nd Battalion The Rifles (2 Rifles) are set to move out of their Co Down base in June and make a new home in Thiepval Barracks in Lisburn.
The move means up to 30 civilian jobs could be at risk at Ballykinler, but the wider economic impact will be felt in the neighbouring towns and villages of south Down where 500 soldiers and their families have boosted local businesses.
The Ministry of Defence (MoD) confirmed the move but said the camp, considered one of the best equipped in the UK, will remain open as an Army training facility.
Rumours of the camp's demise have been circulating for five years but the MoD had previously dismissed speculation about closure and carried out major renovation work at the camp.
A source said there was "surprise and shock" at the news among civilian staff who provide cleaning, catering and security services at the base.
"There was a meeting with the Secretary of State on Thursday and it was decided 2 Rifles was moving and would not be replaced," he said. "The staff were then called together on Friday.
"It is not only the village itself – it is Newcastle, Ballynahinch, Downpatrick, towns like these –that will be affected."
In October there were fears for the welfare of soldiers at the rural base after the suspected suicides of two Afghanistan veterans. There were also reports that restricted movements at the base due to dissident republican activity had heightened feelings of loneliness.
Army Press officer Ken Johnston said the families set to move from Ballykinler were sad to be losing their links with the south Down community but looking forward to living in the more easily accessible Lisburn barracks.
"Ballykinler is going to continue to operate as an Army training facility," he said. "This is about long-term financial best practice.
"There will be an impact on civilian employment and some jobs will not be required long-term. There may be limited opportunity for civilian staff to redeploy. These opportunities have not been worked through."
Mr Johnston said no redundancy numbers had been decided and that "nothing was ruled out" in terms of any future use of the site by another Army battalion.
Two centuries of military history
The Ministry of Defence describes Abercorn Barracks at Ballykinler as "one of the British Army's best-equipped camps".
But now Ballykinler is facing up to the fact that, for the first time in two centuries, it won't be home to an Army regiment.
Soldiers from the base have been part of life in Co Down since Abercorn Barracks were built in 1901, although there was a constant military presence at Ballykinler throughout the century before that.
The Army occupies a stretch of the picturesque south-east Down coastline near the Blue Flag Tyrella beach, which is only passable when no shooting training is on.
The camp was recently brought into use for the World Police and Fire Games.
The sprawling site was used as an internment camp during the Irish War of Independence in 1919 and in World War One the 36th Ulster Division formed from the UVF did much of its training there. During World Ward Two the camp continued as a military training establishment.
It was later used as a training centre by the Ulster Defence Regiment, whose 3rd Battalion was based at Ballykinler.
In 1974, a 300lb IRA van bomb killed two soldiers and destroyed buildings on the base.
In 2008, the 2nd Battalion The Rifles of Ballykinler was deployed on peacekeeping duties to Kosovo. It also fought in Afghanistan.