Very quick brief. Quite some time ago, the entire island of Ireland was one country. The British invaded and took over. Once they had control, the plantation took place where Lords and Knights and whatnot were sent to Ireland in exchange for vast amounts of land (which had been taken from the natives). The area where most plantation took place was in Ulster. After many rebellions from the Irish, an agreement was reached where 26 of Irelands counties became a free state and eventually a Republic. Some were happy with this but a lot were not. Irish Republicans wanted the entire island of Ireland to be one Republic. The recent day conflict is primarily due to this. The Republican paramilitaries were fighting for a united Ireland and the Loyalist paramilitaries claimed to be defending Northern Ireland. Segregation became normal and tensions rose hence the start of the troubles.