An unswerving commitment to Catholicism on the part of the majority, and the frequent uncertainty and instability governing Anglo-Irish relations, are key features of Irish history.
It was a war between the Irish chieftains and the Vikings which first led to the involvement of the English. In 1169-70, Richard of Clare, Earl of Pembroke (nicknamed Strongbow), was invited over by an Irish chieftains to help protect his interests. Instead, Strongbow conquered almost the entire country with only a tiny force of archers and mounted knights.
Many Norman families moved across the Irish Sea, effectively colonising the country. Repeated and largely unsuccessful efforts from the 14th century onwards were made to bring the island under Irish control. The turbulent and increasingly polarised political life of Ireland then took a new twist after the English Civil War, when the Irish rose in favour of the deposed monarchy in 1649. The victorious Oliver Cromwell led an army across the Irish Sea and the rebellion was ruthlessly put down.
The Act of Union in 1801, incorporated England, Scotland, Wales, and the whole of Ireland, into the United Kingdom. However, the grossly inadequate response of the Government to the potato famine of 1845/6 highlighted its lack of interest in the welfare of the Irish people, and Irish Home Rule was granted in 1920. The terms of independence stipulated that Ireland be partitioned into two parts. In the northern provinces, where most Protestants had settled three centuries earlier, there was fierce opposition to the prospect of being ruled by a government drawn from the country's Catholic majority. Six of the nine counties of the historic province of Ulster therefore remained in the United Kingdom, and the other 26 counties became the Irish Free State.
The ensuing civil war in the south between supporters and opponents of the agreement gave rise to the country's two main political parties, Fianna Fáil and Fine Gael. In 1937, the Irish Free State was given full sovereignty within the Commonwealth, and remaining links with Britain dissolved. In 1949, the 26 counties became a republic and formal ties with the Commonwealth were ended. Since the 1970s, Ireland has been governed alternately by Fianna Fáil and a coalition of Fine Gael and the smaller Labour Party.
Recent political agenda has been dominated by the challenge to the orthodox morality of the Catholic Church, especially on the contentious issues of abortion and divorce. Equally contentious is the future of Northern Ireland. Some in Dublin believe that the lowering of barriers between countries, which is a key objective of European Union, will eventually bring about conditions where there is little difference between North and South. Yet many in the North remain deeply suspicious of Dublin's role, and are disinclined to accept anything which may bring North and South closer together.