It isn't completely straightforward any of the Northern Irish stuff though.
The initial problems in the 60s stems from inequality in the province, jobs, housing etc were routinely only given to protestants and catholics were really struggling. There was also gerrymandering of votes on a huge scale (onlt one person per household allowed to vote. That was the reason that the Northern Ireland Civil Rights Association was formed. In the summer of '68 they had their first march, it was around Dungannon, Later that year one was arranged in Derry, which the Norther Ireland government banned, the march went ahead anyway, but the RUC inrecepted it and beat hundreds of the marchers senseless (it was shown on American tv). That caused the first riot in Derry.
6 Months later another group of civil rights activists marched from Belfast to Derry, when it reached Derry it was attacked by over 200 loyalists, including off duty RUC officers, and later that night the RUC went mental in the Bogside area of Derry attacking the residents without any provocation. That was what led to the residents sealing off the area and proclaiming it a no go area called "Free Derry". Ian Paisley's fairly newly formed paramilitary groups were systematically bombing utilities (leaving Belfast without power for a while) and blaming the IRA, which was largely still dormant at the time. That was when British troops were sent to guard power installations.
Then in '69 even though the civil rights marches were still routinely banned the Derry apprentice boys (that's another story, very interesting in it's own right) were allowed to march by the Bogside. Stones and bottles and petrol bombs were thrown from both sides, and the RUC tried to storm the Bogside using water canon, CS gas and armoured vehicles, this turned into the battle of the Bogside.
Around about this time the IRA started to become involved, with people joining them to become involved in protests about the treatment of nationalists. That was when a major IRA sympathiser was killed by the RUC with machine gun fire in Belfast (a 9 year old boy called Patrick Rooney). August '69 was when troops went to Belfast and Derry to restore order, and that stopped the Battle of the Bogside. Also the first RUC officer to be killed in the troubles was shot in Belfast around that same time, he was killed by the UVF after a report suggested they should be an unarmed force (the RUC) and the B specials should be disbanded.
The IRA then split into the Official IRA (in 1971 the Official IRA sanctioned attacks on British soldiers) and the Provisional IRA (their campaign against the military also started in '71) and they took control of a lot of the protests and shored up the barricades in "Free Derry" between 1970 and 1972 or so. The Provisionals, instead of being a nationalist group decided it was to protect the interests of just the catholic community. The government introduced internment without trial during this time and there were huge battles on the Falls Road in Belfast where troops fought against the Official IRA. All of this lot led up to bloody Sunday in 1972.
So it is perfectly understandable that the young soldiers sent out there initially to protect the general public would be absolutely cacking themselves. I certainly would have been, there were threats all around them. However it was caused by the government of Northern Ireland and the UK, the policies (and they were actual policies) of keeping down the catholic working class in the province were disgusting, in a democratic country in the second half of the 20th century, and weren't much better than apartheid in South Africa. It was a real melting pot and it was almost certain to kick off at some stage, people will not take that treatment forever. The rights and wrongs of it all can be discussed forever, but it certainly was not as one sided as it was reported over here.
Between 1969 and 2001, 3,500 people were killed in the troubles (60% by republicans, 30% by loyalists and 10% by the army). The bad crack is that only just over 500 of those killed were paramilitaries on either side. More civilians were killed by loyalist paramilitaries than by republicans, and republican paramilitaries killed as many of their own side as the army and the loyalists managed. It all seems pretty pointless in all honesty, but the crap put out by the press in this country does not come close to what actually happened, there are now 6 or 7 families on either side in Belfast who want it all kept going (so I was told by the former mayor of the city last time I was there) and the vast majority of the population want peace. It is nowhere near as bad as what it was, but arresting former British troops is not at all helpful, and could quite easily bring back some former tensions, I don't see ant good reason why this should be done.