The capacity of the Army in the event of a Doomsday situation in 1970 was limited to holding the town of Newry, Co Down, for as little as 24 hours and considerable casualties were anticipated in such an operation. State papers for that year also make clear the authorities had a "mercy mission" rather than an invasion of the North in mind.
At a meeting on June 9th, 1970, with the Taoiseach, Jack Lynch, and Jerry Cronin, who had succeeded James Gibbons as minister for defence, the Chief-of-Staff, Lieut-Gen Sean McKeown, stressed the urgent need for "clear-cut governmental policy on defence".
The Army notes of the meeting continue: "In view of the reiteration of Government policy from time to time regarding the aim of reunification of the national territory by peaceful means, no military studies had been undertaken nor had plans been prepared even on a contingency basis for military action in Northern Ireland prior to August 1969."
In relation to the governmental "direction" of February 6th to the Army to prepare for possible incursions into Northern Ireland, the Taoiseach confirmed such operations would only be mounted where the lives of the minority were in grave danger and the security forces in Northern Ireland were unable or unwilling to protect them.
"Regarding the use of the word `incursion', the Chief-of-Staff explained this term had been used in conveying the Government directive and that it conveyed to him that cross-Border activity was not intended as an invasion, but rather as a short temporary stay to carry out a mercy mission and return."
The document continues: "The Chief-of-Staff indicated that a military study had been completed involving an incursion to Newry. This Northern town, although considered to be close the Border, is considered as the extreme limit of incursion capability at present strength and status of supply. The study indicated that some 800 troops would be necessary for such an operation; that the stay might well have to be limited to 24 hours at most and that even then considerable [the word `heavy' is crossed out] casualties could be anticipated."
In response, the Taoiseach "reaffirmed that it was the policy of the Government that force would NOT [capital letters in the original] be used as a means to reintegrate the national territory". Mr Lynch added he had given considerable thought to the possibility that Irish troops could work in conjunction with British troops in the event that a situation would arise in the future in which the British troops would be unable to defend the minority. However, in response to a query from Lieut-Gen McKeown, the Taoiseach indicated that incursions into the North "would not be preceded by political or diplomatic representations."
The document adds, "The Taoiseach was aware of meetings which took place between the General Staff and Mr Gibbons and Mr Haughey".