Four different emergency situations in Northern Ireland requiring cross-border intervention by the Defence Forces were the subject of a feasibility study by a military planning board as early as September, 1969 - the month after serious violence erupted.
The board's interim report, marked "Secret" and dated September 27th, has been released for public inspection as part of the 1970 State papers in the National Archives. The board "would have liked a clearly-defined political objective" but in its absence decided to consider a number of scenarios, "each of which might suggest military intervention".
The four situations considered were: (a) "attacks on the Catholic minority by Protestant extremists with which the Northern Ireland security forces cannot cope; (b) conflict between the Catholic minority and the Northern Ireland security forces on civil rights issues; (c) conflict between republican-nationalist elements (possibly supported by illegal elements from south of the Border) and the Northern Ireland security forces; (d) conflict between Protestant extremists and Northern Ireland security forces not directly involving the minority."
In each situation it is assumed that unilateral action by the Defence Forces would "meet with hostility" from Northern Ireland security forces. "The Defence Forces have no capability to engage successfully in conventional offensive military operations against the security forces in Northern Ireland at unit or higher level," the report continues. Such operations would be hazardous "in the absence of armoured personnel carriers, fighter aircraft and air defence weapons".
The study opts instead for a mix of small-scale conventional operations and "unconventional", i.e., guerrilla-type, activity. In addition, the Defence Forces would be capable of: "(1) organising and conducting military training in the Republic for nationalists living in Northern Ireland; (2) supplying arms, ammunition and equipment in accordance with availability to nationalist elements in Northern Ireland."
Conventional operations would be confined to areas with a Catholic/nationalist majority. In areas where nationalists were a minority, particularly Belfast, only unconventional operations could be conducted. "It is to these latter areas that supplies of arms and equipment should be chiefly directed."
The existence of a common border and good road network would facilitate cross-border operations: "However, in the light of modern surveillance techniques available to the security forces in the North, guerrilla-type operations in Northern Ireland would be difficult to conduct over a protracted period."
The report notes: "The majority of the more important vital installations in Northern Ireland, e.g., Belfast Airport, TV studios, docks and main industries are located in the North-East corner, some distance from the Border. Any military operations conducted against these should preferably be of the unconventional type."
In Situation A, where the minority was under attack by loyalists, it was proposed to move troops into Newry and the nationalist part of Derry; use guerrilla activity to ease the pressure on other nationalist areas; supply arms and equipment to Catholics under attack.
In Situation B, where nationalists were under attack by the Northern Ireland security forces, conventional military activity in their defence was envisaged, along with the supply of arms and "a wide range of unconventional operations". A similar approach was envisaged in the Situation C (conflict between nationalist-republican elements and the security forces) "plus the following: organising training for nationalist-republican elements".
In Situation D (conflict between loyalists and the northern security forces not directly involving nationalists), the plan was: "(a) infiltrate elements armed and equipped to organise, train and advise Catholic and nationalist groups in vulnerable areas far from the Border (e.g., Belfast); (b) deploy sub-units up to company level across the Border prepared to keep routes open for refugees moving south."
The report comments that a general training programme was needed, including "specialised skills required for unconventional operations such as demolitions, communications, street fighting and riot control".
It could not be assumed that troop morale was high: "Esprit de corps is virtually non-existent in the Infantry Corps, which in the present situation would be a key element". However it was possible that "the motivation generated in going to assist one's countrymen might bring about an increase in individual and unit morale".
A cautionary note was struck concerning the prospect of working with civil rights and republican groups in the North because this could also lead to co-operation with illegal groups in the Republic: "These contacts would have serious political implications on the national and international scene.
As part of a series of recommendations, the board suggests the establishment of a Special Forces Unit for guerrilla operations and "a motivation programme . . . aimed at indoctrinating our own troops".
A further report dated October 10th notes that, in the case of an emergency, "troops operating in Donegal could be isolated by British action across the Border from Belleek to seize Ballyshannon."
A third report, dated April 6th, 1970, and entitled "Military Commitments and Requirements", was prepared after the February 6th Government directive to the Army to train and prepare for possible incursions into Northern Ireland.
Apart from the British-controlled military forces and police in Northern Ireland, the document notes that "there is a considerable partisan element and arms are available for a majority of a hostile population."