The main reason conflict has broken out in Northern Ireland is because of its unification issues. There was a divide between unionists, usually people who wanted to remain within the United Kingdom and were protestants and the nationalists who wanted to unify with the Republic of Ireland and were Catholics. There was constant tension as it was said the unionists mistreated the nationalists and violence soon broke out. Although the Northern Ireland conflict is technically supposed to be finished, sporadic violence still breaks out.
The Holocaust lasted from 1941 till 1945 however Jews were being killed in Germany since 1933, so it would be 1933 to 1945 and that makes 12 years. Approximately 5 and 6 millions Jews were killed, 1.5 million were children. But it's impossible to exactly how many Jews were killed since their deaths were in different events such as the concentration camps (ex: Auschwitz)
People were still rascist, so it made more sense leave rather than stay and be discriminated and even killed.
portal: Libraries and the Academy 2.1 (2002) 99-123 In November 2000, the Digital Library Federation (DLF) and the Council on Library and Information Resources (CLIR) commissioned a white paper to initiate discussion of how and why libraries are changing. Eight academic library directors met with representatives from the DLF and CLIR in March 2001 to discuss the issues.