Was there widespread support for the IRA, or did the general population condemn the violence? What did the major politicians say about the situation in ulster/northern ireland? How did it affect the population of Ireland in their opinion of peaceful reunion? What changed for the economies of the IRA controlled afterwards, and the people?
Generally there was a lot of support for Irish unification, however a large amount of the southern population felt that the methods of the IRA went to far and supported non-violent groups such as the later Sinn Fein and SDLP parties. However two notable politicians 'Charles Haughey and Neil Blaney' respectively ministers for finance ,and agriculture and fisheries were accused of arms trafficking in the 'arms crisis' of 1970 (http://en.wikipedia.org/wiki/Arms_Crisis) they were let off the charges against overwhelming evidence, suggesting a sympathetic court system and also sympathetic figures in the higher reaches of the Irish government. Haughey was also later elected as Taoiseach (essentially prime minister or to American readers just the leader of Ireland as the president also exists but performs less important duties) giving evidence to the Irish support for the Northern Republicans. http://en.wikipedia.org/wiki/Charles_Haughey However this is coming from a mainly Unionist source and perhaps it would be good to also find a nationalist historian. I would personally recommend 'History' by Adam Hart Davis for further reading. It only has a few pages on Northern Ireland but an excellent source overall.
Hopefully this answers some of your question. I don't have the most in depth knowledge of this topic, but I think I know enough that I can shed some knowledge on.
Anyway, this is a really complicated that needs some background first.
The National Identity Conflict actually played a large role in the separation of Irish vs. English people. While the English saw the Irish as citizens of England, the Irish saw themselves as citizens of Ireland. Between religion, culture, and beliefs, the two were fundamentally different which was discovered through the Social Identity Theory.
The ultimate goal was to gain independence from the British Crown. The Irish wanted to form a new parliament that was run solely by Irish people, because they were vastly under-represented in British Parliament. They felt the British rule was not working in the best interests for the Irish people, which is why they wanted their own parliament.
Now, there was not entire support of the Irish revolt. Unionists, who saw themselves as British citizens living in Ireland, opposed Irish independence, which greatly increased the tension between England and Ireland due to the proximity of the crown supporters. So, this led to the proposal of the Home Rule Bill, which would give Britain sovereignty over all territories under parliament's authority, and helped the surge of the Irish joining the war. The British said they would give independence to the Irish if they fought in the war, but the problem was, unfortunately, that the Irish would have to fight in the war. Part of joining the military was pledging an oath to King George, which was exactly why they wanted to revolt. There was a theory that it would turn into a civil war, which was the last thing that Britain needed during a global war. Despite this theory, the bill still passed.
Now, the Easter Uprising was where the first real violence occurred in the Irish struggle for independence. This was executed by the nationalist and Protestant forces against British authority, and they demanded unconditional surrender granted their position. This really showed how serious the Irish were in rebelling, and it marked the change from a diplomatic secession to a militaristic. It also caused some controversy in the Conscription Crisis.
To get on to your question now, the rise of the Irish Republican Army formed and basically facilitated the rest of the rebellion. There was a lot of support for the IRA, including the Irish Republican Brotherhood, the Irish Citizen Army, the Irish National Militia, Jack Connolly's Army, and some other pro-nationalism groups. The IRA started using guerrilla tactics against British forces in the Anglo-Irish War, which turned out to be pretty easy because Britain was in its post-war years and was not ready to fight another war. The IRA eventually turned to killing very prominent figures that were crucial to the success of Great Britain simply as a country. Essentially, the IRA was so focused on fighting against the British that it did not stop and look at the devastation that it was causing to the country it was fighting to protect. The support of the Sinn Fein movement, which was obviously a left-wing group, was highly encouraged by the IRA. Eventually, England gave in and gave the nationalists their own free state.
One thing to mention was a British General Sir John French came in after being relieved from his involvement in the Great War and was sent to Ireland to contain the revolution. He used brutal tactics and killed many Irish nationalists, which may have affected the population immensely.
Quickly after the treaty was signed, there was a lot of strife between some major figures and parties in Ireland. The provisional government that was established as the free state was seen as a betrayal to the republicans for the idea of an Irish Republic. This split a lot of the IRA forces, into two groups, the National Army and the other half stayed as the IRA. However, this time, the IRA did not have the support of the people nor the resources to use at their disposal that they previously had.
In 1931, there was an uprising of IRA violence, and raids of arming stations and weapons caches. There also came the Fianna Fail movement, which was against the free state. They also dealt with economic issues that caused them to default on loans that were owed to the British. The British, in turn, imposed heavy taxes on Irish imports, which caused many resentful opinions within Ireland.
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