Britain's Queen Elizabeth starts a four-day state visit to the Irish Republic on Tuesday, the first visit by a British monarch since King George V in 1911.
The visit will confirm warm ties with Ireland.
Ireland became independent from Britain in the early 20th century, though Britain retained the north of the island. Here are details of the historical roots of Anglo-Irish relations:
* English King Henry II landed in Ireland in 1172 after winning support from the pope to become its overlord. The next five centuries were marked by repeated battles for control.
* In the 14th century, the Crown tried to prevent English settlers integrating with the locals by outlawing the Irish language and making intermarriage illegal.
* Battles for Ireland have had a religious dimension since the 1530s, when England's King Henry VIII broke with Roman Catholicism to found the Protestant Church of England. Catholic estates in Ireland were dissolved and the land given to the king's supporters. A 1534 revolt was crushed.
* In the reign of Henry's daughter Elizabeth I, more British aristocrats took over estates in Ireland in a colonization, or "plantation," policy justified as a moral crusade to turn Gaelic Irish away from Catholicism. A rebellion led by Hugh O'Neill was thwarted in 1603.
* Settlers from Scotland came to Northern Ireland in large numbers under King James I. They were allowed to buy up grants of land very cheaply in the early 17th century.
* In 1649 Oliver Cromwell, a strict Protestant who had taken power in England after a civil war, landed in Ireland with 3,000 men and overran the country, killing one quarter of Ireland's Catholics. A reviled Penal Code barred Catholics from teaching, owning land, voting or serving in the military.
* In 1690 Catholics were defeated by England's Protestant King William III -- William of Orange -- at the epic Battle of Boyne. Ulster Protestants still call themselves Orangemen and commemorate the battle.
* The Irish parliament was abolished by Britain in 1801, heralding a century during which demands grew steadily for Irish home rule.
* The horrific potato famine of 1845 cut the Irish population by at least 2 million through emigration and starvation, and fueled hatred of absentee landlords who levied high taxes on their malnourished workers.
THE 20th CENTURY:
* In 1905 Sinn Fein ("We Ourselves") became a political party committed to Irish independence. Ireland's main political parties today, Fianna Fail and Fine Gael, both would later emerge from Sinn Fein.
* In April 1916, a band of nationalists in Dublin led the abortive Easter Rising against British rule. They were forced to surrender by British artillery shelling and leaders were court-martialled and executed, releasing a wave of anger toward the British authorities.
* Eamon de Valera, the senior survivor of the rising, led Sinn Fein to win a majority of Ireland's seats in the British parliament in the election of 1918. Instead of joining the British parliament, they formed their own assembly, which declared independence. An Anglo-Irish war followed.
* The British government partitioned the island in 1921, separating Northern Ireland with its "loyalist" Protestant majority from predominantly Catholic Ireland.
* The 1921 Anglo-Irish Treaty between a delegation of Irish pro-independence leaders and Britain established the Irish Free State, a self-governing dominion within the British Empire, in 1922. Northern Ireland remained part of the United Kingdom.
* De Valera refused to accept the treaty. Ireland was plunged into civil war between supporters and opponents, who believed the treaty did not do enough to secure independence.
* Ireland broke its remaining ties with Britain at the end of 1937 with a new constitution that replaced the Free State with the modern state of Ireland. The 1948 Republic of Ireland Act declared Ireland a republic, ending its status as a dominion of the British crown.
* Many members of the Catholic minority in British-ruled Northern Ireland have continued to seek the unification of the island, while Protestants favored continued British rule. Between the late 1960s and 1990s, a period known as "The Troubles," about 3,600 people died in violence there, which largely ended with a peace agreement in 1998.
Sources: Reuters/www.britannica.com/Penguin Dictionary of 20th Century History/
(Writing by David Cutler; Editing by Peter Graff; London Editorial Reference Unit)