Additional armed gardaí are being posted to the Border in the New Year.
The decision to boost the strength of Special Branch and Armed Support Units (ASUs) has been fast-tracked by fears of a hard border post-Brexit.
Garda Commissioner Drew Harris and his security advisers are concerned about the problems that could arise with a hard Brexit acting as a recruiting weapon for dissident republican gangs.
The move follows a review by senior officers at Garda headquarters of the existing armed strength in the region.
Two ASUs are currently deployed in Ballyshannon, Co Donegal, and Dundalk, Co Louth, and are tasked with providing armed intervention and support for the northern region, which covers the Border.
Now security chiefs have decided to create a third ASU, which will be based in the Cavan-Monaghan division.
It has also been agreed to deploy more Special Branch teams, from their headquarters at Harcourt Square, Dublin to bases in the northern region to help cope with the potential security problems that will arise from a British no-deal departure.
"Our armed units are stretched at present to cover an area from Donegal across to Louth and this decision would have been introduced anyway, as a result of the review," a senior officer said.
Contingency planning for Brexit by gardaí under Assistant Commissioner Michael O'Sullivan, who is in charge of national security and intelligence for the force, is well advanced and covers options that could be adopted by the UK as they exit the EU.
A no-deal Brexit, which could result in the re-introduction of customs posts, will put the biggest strain on garda strength in the Border divisions and PSNI manpower.
The British government has given approval to PSNI Chief Constable George Hamilton to launch recruitment to increase the strength of his force by 300 new officers and staff. However, Taoiseach Leo Varadkar has said there are no similar contingency plans here. Gardaí said a lot would depend on the reaction from both republican and loyalist communities to Brexit.
Intelligence indicates dissident republican gangs are monitoring to see if they can exploit any opportunities to create mayhem and use the return of customs posts as a recruitment tool while increasing cross-Border smuggling rackets to boost funds.
Several key figures in dissident terror groups are due for release from Portlaoise prison in the coming months.
Most of the main groups are leaderless and their hierarchy structures have collapsed because the gardaí have put leading terrorists behind bars. Internal struggles have also reduced their effectiveness.
The so-called OnH group, once regarded as posing one of the most serious threats to security, has split into three factions following the declaration of a ceasefire last January.
A relatively new group, called Arm na Poblachta, has emerged in the North but is not a player on this side of the Border.
Longer-term republican terrorists in the Donegal-Derry area continue to run their own activities there though they have some links with the New IRA.
The combined strength of the dissident republican groups is estimated at between 300 and 400 and all have been infiltrated by the garda's specialist units.