From the late Middle Ages until the 1800s, the whole of Ireland was ruled as a separate entity under the British crown. After 1800, it became an integral part of the United Kingdom. During the Easter Week Insurrection of 1916, Irish nationalists first proclaimed the Republic of Ireland. Their revolution was initially crushed by the British, but in 1919 they reasserted Irish independence.
In the Anglo-Irish treaty of 1921, the Irish Free State was established. In the north, Protestant loyalists (loyal to Great Britain) insisted on remaining part of the United Kingdom while retaining limited self-government. The country was thus divided into the northern six counties that became Northern Ireland and the 26 remaining counties that make up the Republic of Ireland.
In 1937, a new Constitution of the Irish Republic was enacted. Association with Great Britain was gradually loosened, and, when the government of the Republic of Ireland repealed the External Relations Act in 1948, the last link to the British crown came to an end.
Since the late 1960s, civil unrest in Northern Ireland -- initially in pursuit of civil rights for Roman Catholics and subsequently the violent activities of the illegal Irish Republican Army (IRA) -- has greatly complicated relations between the Republic of Ireland and Great Britain.
The original IRA was part of the revolutionary movement that brought independence to the Irish Republic. Today's IRA, outlawed in both the Republic and Northern Ireland, is a group that uses violence and terrorism to oppose the division of the country and the presence of Britain in Ireland.
In 1969, clashes between civil rights demonstrators and Ulster police prompted Great Britain to send troops in to reestablish order and to protect the Catholics in Ulster, which is predominantly Protestant. Today's ``provisional'' IRA was formed in response to this and succeeded in turning many of Ulster's Roman Catholics against the British presence. IRA activists used the Republic as a haven from the security forces in Northern Ireland, and the ``border issue'' became a source of friction between the Republic and British governments.
The murder in in the Republic in 1979 of Earl Mountbatten of Burma, a prominent British public figure, and the massacre of 18 British soldiers at Warrenpoint in Northern Ireland prompted the Republic of Ireland to further tighten up its own security measures and increase security cooperation with Britain.
In 1981, hunger strikes by IRA members imprisoned in Northern Ireland led to more violence and pressure to find a solution. One result came in the formation of the Anglo-Irish Inter-Governmental Council, to meet at ministerial and official levels concerning Ireland's future.
The November 1985 signing of the Anglo-Irish Agreement gave the Irish Republic a consultative voice in the government of Northern Ireland. In protest against this accord, 15 Unionists (members of allied parties favoring union with Britain) resigned their seats in the British Parliament, forcing by-elections to take place on Feb. 23, 1986.