The IRA killed border protestants to keep the SDLP and UUP apart

Henry Patterson wrote:

"Gerry Adams was particularly concerned to ensure that no deal was developed between the Ulster Unionists and the moderate Nationalists of John June’s Social Democrats and Labour Party (SDLP) which would have marginalised republicans. As one Tyrone republicans explained to the journalist Ed Maloney, the killing of UDR men “stops the unionists doing a deal with the SDLP”. It was also the case that “Ulsterisation”, by cutting down on the number of British soldiers available as targets, meant the Provisionals had an added incentive to target the RUC and UDR. The establishment of Adam’s henegmony in the republican movement by the end of the 1970s coincided with an intensification of attacks on the UDR in border areas. South Fermanagh was particularly affected."

Professor Henry Patterson published 'Ireland’s Violent Border' in 2013 about the sectarian murder campaign carried out by the Provisional IRA in the border areas of Northern Ireland. Patterson explained his reasons for writing the book:

"I wanted to write about the border, the problems of north-south security co-operation and the terrible price which border Protestant communities paid for it, because it’s a crucial, but largely ignored, story. 

It’s very common in literature on Northern Ireland and the Troubles to see it largely in terms of a dominant Protestant majority and a Catholic minority, but in the border areas it was the Protestants who were in the minority and who suffered for it. 

It has been ignored in large part because it does not fit into the oppressive Protestants/oppressed Catholics dichotomy."

He further said:

"The British were convinced that the IRA's ability to exploit the Border and use the Republic as a safe haven was the key to the Provos' ability to wage the long war but with the exception of the Fine Gael/Labour coalition of 1973-77 the Irish default position was that most of the violence in NI had its origins there and the Republic's contribution to the the violence was minimal. The British sent regular security analyses of the Provos' exploitation of the Border and Irish territory to Dublin and pleaded for more co-operation but, particularly when Fianna Fail was in power, it got a cool reception. 

Both Lynch and Haughey made it clear that the price of improved co-operation from Dublin would be high – a major constitutional initiative by London in tandem with Dublin and over the heads of unionists. The result was outlined by a former RUC Special Branch officer referring to the Provos' infrastructure in the Republic in 1980s: 'My conclusion: while successive Irish governments proclaimed their abhorrence of Provisional violence, their refusal, with the partial exception of the Fine-Gael coalition of 1973-77, to take the issue of Provisional exploitation of their territory seriously, objectively facilitated the organisations' ability to carry on its long war into the 1990s.'"