Ireland was part of the United Kingdom of Great Britain and Ireland from 1801 to 1922. For almost all of this period, the island was governed by the UK Parliament in London through its Dublin Castle administration in Ireland. Ireland faced considerable economic difficulties in the 19th century, including the Great Famine of the 1840s. The late 19th and early 20th centuries saw a vigorous campaign for Irish Home Rule. While legislation enabling Irish Home Rule was eventually passed, militant and armed opposition from Irish unionists, particularly in Ulster, opposed it. Proclamation was shelved for the duration following the outbreak of World War I. By 1918, however, moderate Irish nationalism had been eclipsed by militant republican separatism.
In 1919, war broke out between republican separatists and British Government forces. In 1920, the British Government partitioned Ireland into two semi-autonomous regions: Northern Ireland and Southern Ireland, intended to be co-ordinated by a Council of Ireland. Upon Royal Assent, the Parliament of Northern Ireland came into being in 1921. However, the institutions of Southern Ireland never became functional. On 11 July 1921, a ceasefire was agreed between the separatists and the British Government. Subsequent negotiations between Sinn Féin, the major Irish party, and the UK government led to the signing of the Anglo-Irish Treaty which resulted in five-sixths of Ireland seceding from the United Kingdom.
