Partition of Ireland
The partition of Ireland () divided the island of Ireland into two distinct jurisdictions, Northern Ireland and Southern Ireland. It took place on 3 May 1921 under the Government of Ireland Act 1920. Today the former is still known as Northern Ireland and forms part of the United Kingdom, while the latter is now a sovereign state also named Ireland and sometimes called the Republic of Ireland.
Northern Ireland Office
Before the partition, Ireland was governed through the Dublin Castle administration and the Home Office was also responsible for Irish affairs. From 1924 to 1972, Northern Ireland affairs were handled by the Northern Ireland Department of the Home Office. In August 1969, for example, Home Secretary James Callaghan approved the sending of British Army soldiers to Northern Ireland.