Partition of Ireland
Beginning on 21 January 1919 with the Soloheadbeg ambush, through the Irish War of Independence, Irish republicans attempted to bring about the secession of Ireland from the United Kingdom of Great Britain and Ireland. Meanwhile, Irish unionistsmost of whom lived in the northeast of the islandwere just as determined to maintain the Union. The British Government, committed to implementing Home Rule, set up a cabinet committee under the chairmanship of southern unionist Walter Long. The Long Committee recommended the establishment of two devolved administrations, dividing the island into two territories: Northern Ireland and Southern Ireland. This was implemented as the Government of Ireland Act 1920. The act entered into force as a "" on 3 May 1921 and provided that Northern Ireland would consist of the six northeastern counties, while the remainder of the island would form Southern Ireland. It was intended that each jurisdiction would be granted home rule but remain within the United Kingdom. The government of Southern Ireland never functioned: the war for independence continued until the two sides agreed a truce in July 1921, ending with the Anglo-Irish Treaty on 6 December 1921.
Northern Ireland
The region that is now Northern Ireland was the bedrock of the Irish war of resistance against English programmes of colonialism in the late 16th century. The English-controlled Kingdom of Ireland had been declared by the English king Henry VIII in 1542, but Irish resistance made English control fragmentary. Following Irish defeat at the Battle of Kinsale, though, the region's Gaelic, Roman Catholic aristocracy fled to continental Europe in 1607 and the region became subject to major programmes of colonialism by Protestant English (mainly Anglican) and Scottish (mainly Presbyterian) settlers. A rebellion in 1641 by Irish aristocrats against English rule resulted in a massacre of settlers in Ulster in the context of a war breaking out between England, Scotland and Ireland fuelled by religious intolerance in government. Victories by English forces in that war and further Protestant victories in the Williamite War in Ireland (1688–1691) toward the close of the 17th century solidified Anglican rule in Ireland. In Northern Ireland, the victories of the Siege of Derry (1689) and the Battle of the Boyne (1690) in this latter war are still celebrated by some Protestants (both Anglican and Presbyterian).
Popes Innocent XI and Alexander VIII had supported William of Orange instead of his maternal uncle and father-in-law James II, despite William being Protestant and James a Catholic, due to William's participation in alliance with both Protesant and Catholic powers in Europe in wars against Louis XIV (the "Sun King"), the powerful King of France who had been in conflict with the papacy for decades. In 1693, however, Pope Innocent XII recognised James as continuing King of Great Britain and Ireland in place of William, after reconciliation with Louis. In 1695, and contrary to the terms of the Treaty of Limerick (October 1691), a series of penal laws were passed by the Anglican ruling class in Ireland in intense anger at the Pope's recognition of James over William, which was felt to be a betrayal. The intention of the laws was to materially disadvantage the Catholic community and, to a lesser extent, the Presbyterian community. In the context of open institutional discrimination, the 18th century saw secret, militant societies develop in communities in the region and act on sectarian tensions in violent attacks. These events escalated at the end of the century following an event known as the Battle of the Diamond, which saw the supremacy of the Anglican and Presbyterian Peep o'Day Boys over the Catholic Defenders and leading to the formation of the Anglican Orange Order. A rebellion in 1798 led by the cross-community Belfast-based Society of the United Irishmen and inspired by the French Revolution sought to break the constitutional ties between Ireland and Britain and unite Irish people of all religions. Following this, in an attempt to quell sectarianism and force the removal of discriminatory laws (and to prevent the spread of French-style republicanism to Ireland), the government of the Kingdom of Great Britain pushed for the two kingdoms to be merged. The new state, formed in 1801, the United Kingdom of Great Britain and Ireland, was governed from a single government and parliament based in London.