One-tenth of British soldiers recruited in Northern Ireland last year came from the Republic.
Closer cross-border political links and economic conditions are among the chief reasons for the growing numbers from the Republic signing up, according to officers in charge of enlisting.
At the height of the troubles there were up to 30,000 British troops based in Northern Ireland, but with the end of the IRA's campaign and the developing peace process the level has dropped to just 3,000.
Lieutenant Colonel Dick Rafferty, head of British Army recruitment in Northern Ireland, said: ‘Given the current strong and vibrant political relations between north and south there is less of a stigma in telling your friends and family that you've joined.
‘Perhaps we are seeing old prejudices and preconceptions being put to one side or erased.’
He added the number of those enlisting from the Republic had been growing since 2003 with the proportion more than doubling last year.
For many years the number of recruits from the Republic was in decline.
However, 4.5% of recruits came from the Republic of Ireland in the financial year ending March 2007 and 10.5% the following one.
Lt Colonel Rafferty said there were now more positive views on military service.
He said that economic conditions can also play a part, but he added that he suspects there is a strong word of mouth endorsement from serving soldiers telling about their experiences when they go home.
Wicklow man Lieutenant Paddy Bury from the Royal Irish Regiment, serving in Afghanistan, said: ‘(Irishmen) join for a sense of self-worth, challenge, adventure, travel and above all camaraderie.’
A spokesman for the Defence Forces in Dublin said they were satisfied with their own intake.
There are 10,500 members of the Irish army, navy and air corps.
He said that they recruit 600 people a year and recruitment competitions are generally over-subscribed.
