Jim,
And still no references to the cause of the Troubles and none expected

This is the answer Cain provides,

"What is the main cause of all the trouble in Northern Ireland? Is religion a big part of it?
The conflict in Northern Ireland is usually explained in terms of the different constitutional aspirations of the two main sections of the community in the region. Many Catholics consider themselves to be Irish and are Nationalist in political outlook, that is, they would like to see the whole (nation) island of Ireland reunited (and independent of Britain). Most Protestants consider themselves to be British and are Unionist in political outlook, that is, they want Northern Ireland to remain part of the (union of the) United Kingdom (UK) of Britain (England, Scotland, and Wales) and Northern Ireland. "

So the problem was that the majority of the people did not want to be part of the Republic, but the Republicans were determined to force them to be by murder and intimidation, since they would never vote for it.
The Troubles ended when the demand for a united Ireland was dropped.