In 1801 Ireland and Britain were formally joined under the title of the United Kingdom. After decades of agitation, a home rule bill was passed at Westminster in 1914, but suspended because of the outbreak of war. An armed uprising in Dublin on Easter Monday 1916 was put down by the British. Continuous armed conflict between 1919 and 1921 forced Britain to agree to Irish independence. On 6 December 1921 the Irish Free State was established under the British Crown, excluding the six northern counties which remained part of the UK. A civil war followed, between republicans opposed to partition and those who accepted British terms.

A new constitution was introduced in 1937, severing the remaining links with Britain and establishing the independent republic of Eire. The country remained neutral during World War II. In April 1949 a new constitution took Eire out of the Commonwealth and created the Republic of Ireland. Ireland joined the European Community (EC) in 1973. Since 1969, republican terrorist activity close to the border with Ulster ('Northern Ireland') has become a major security problem. The terrorists stated aim is a marxist united Ireland.

On 10 April 1998 the Belfast Agreement ('The Good Friday Agreement') was signed by Ireland and the United Kingdom. This agreement provides for the Irish Government to participate in certain aspects of the running of Northern Ireland. Increased prosperity due to membership of the European Union, and the implementation of the Belfast Agreement has undermined support for terrorist groups and security has improved markedly.