The violence also lead on from longer running causes. There was anger over what the British had done to Ireland in the past. 77 people were sentenced to death in 1916 due to their actions in the Easter Rising. Before the sentencing there had been no popular support for the rebels, but this punishment angered many Catholics in Ireland. There were acts committed even longer ago, such as in 1649 when Oliver Cromwell’s army slaughtered Catholics; 3500 people, including civilians, prisoners and Catholic priests, were killed after the capture of Drogheda. There was also resentment on the protestant side due to the partition of Ireland in 1920.
The police weren’t adequate to control the violence. The police force was composed almost entirely of Protestants, causing them to sometimes act in a biased way (they did little to stop the stoning of Catholics in the Belfast to Londonderry march). There were also the B Specials, who were completely Protestant, who were involved in many of the attacks on Catholics such as the attack on Bogside in January 1969.
People within the British government believed that the troops would be able to control the violence. According to Roy Hattersley’s memoirs Bernadette Devlin, leader of one of the civil rights campaigns, said that, unless troops were sent into Derry, Catholics would be slaughtered. This is part of the reason that some people wanted the troops sent in. Hattersley’s memoirs also state that the Royal Ulster Constabulary requested that soldiers be sent to aid the police. Hattersley said he made the decision to send troops in because it was the only decision possible with both the Chief constable and Bernadette Devlin supporting the idea.
Whenever there had been trouble in the past the British had sent troops into Ireland, such as when soldiers were sent in against the Easter Rising in 1916.
Sending troops in was also what many other countries did in response to this type of violence. This is what happened in the French student riots in May 1968 (less than a year previously) and the Black Civil Rights movement in America, also taking place in the previous year (Martin Luther King was shot on the 4th of April 1968 - the previous year).
Fear was an important factor in the introduction of the soldiers. The violence originated from Protestants fearing that if the Catholics got more civil rights it might aid the nationalists who wanted a united Ireland. And the troops were sent in due to fear that civilians would get harmed (like Bernadette Devlin’s fears that either Protestants or the police would kill Catholics).
Soldiers were sent into Northern Ireland in 1969 due to a combination of factors, all of them important in how they contribute to the decision. There was violence and it was too much for the police to control, so someone else had to control it. The British government sent troops in because they thought it would control the violence and sending soldiers had many precedents. No one factor alone lead to the troops being sent in.