Most conflicts begin for simple, clear reasons, then get murkier and more complex over time. The conflict between England and Ireland began over simple geography. Events made it into a veritable cauldron of geography, religion, nationalism, empire and rebellion.

Geographical Issues

The Emerald Isle, as Ireland is sometimes called, lies directly west of England. In the never ceasing wars over territory between the great powers of Europe during the middle of the last millennium, Ireland never played a great role. England, was, however, a major player, so countries engaged in primary disputes with England sometimes inflamed Irish rebellion to distract England. King Henry VIII was technically the Lord of Ireland upon his succession to the English throne in 1509 but had little practical influence outside of Dublin. In the early 1530s, Henry VIII sent an army to invade Ireland to put an end to rebellious distractions there. This was the beginning of the Tudor Conquest, which played out over 60 years, much longer than Henry or anyone else in England expected.

Religious Conflict

The Tudor Conquest began in the midst of the Reformation, when many Christians withdrew from the Catholic Church to form a new Protestant Christianity. Henry VIII originally resisted the Reformation, but when he could not get the Catholic Church to annul his marriage, he formed a new Protestant denomination, the Anglican Church, with himself as its head. In 1536, Henry declared Ireland to be an Anglican country, along with the rest of Great Britain. Ireland had been a passionately Christian country, which -- before the Reformation -- meant it was a passionately Catholic Country. When members of the disfavored Catholic religion were barred from public honors or offices unless they converted, this added a religious dimension to the conflict.

Imperial Usurpation

Resistance to the new Anglican religion proved so intractable in Ireland that England began granting substantial privileges and grants of lands and licenses to Protestants from England and Scotland who moved to Ireland. Most settled in Ulster, making it a Protestant stronghold in a Catholic Country. But it was a stronghold seen by much of the rest of the country as consisting of foreign usurpers. This inextricably intertwined the religious dispute with a burgeoning nationalist dispute. As the Reformation continued, some small enclaves of non-Anglican Protestants made common cause with the Catholics both for nationalist reasons and because they were almost as rigorously oppressed as the Catholic dissidents.

Nationalist Rebellion

Within a few generations, descendants of the original Protestant immigrants considered themselves fully Irish. Many had never been to England. They considered theirs a nationalist cause, while depending on England to protect their privileges and lands against the demands of the more ancient and abundant Catholic population. Though the conflict remained a fundamentally nationalist one, almost all those pressing for Irish independence were Catholic and lower class. Almost all of those pressing for loyalty to the British Crown were the more affluent Protestant descendants of those sent to colonize Ireland. So the dispute came to be seen as strife between variations of Christians.

Uneasy Co-existence

As recently as the 1970s, both England and Northern Ireland were frequently scenes of carnage and violence as the dispute continued to rage. In 1921, 26 of Ireland's 32 counties were declared free states with dominion status by the British Parliament, formalized as a republic in 1946. The six counties in Northern Ireland that were not included were the economic and manufacturing heart of Ireland, which is why the dispute and violence gravitated there. Finally, in the last decades of the 20th century, Irish Republicans agreed to stand for election to seats in the Northern Ireland Assembly. With an independent republic in the lower 26 counties and genuine representation in the Northern Irish Assembly, the violence calmed to an uneasy truce.