The border between Northern Ireland and the Republic of Ireland (formerly the Irish Free State) was created in the early 1920s, at a time when a lot of national borders were being drawn and redrawn after World War I. The border in Ireland emerged out of a long-standing conflict between nationalists who sought varying levels of independence from Britain, and unionists who wanted Ireland to remain part of the United Kingdom.

Home Rule

From the second half of the nineteenth century and into the beginning of the twentieth century, Irish nationalists campaigned for ‘Home Rule’ – a parliament in Ireland which would have control over domestic affairs. Irish unionists were opposed to Home Rule for several cultural, economic, and political reasons. Under Prime Minister William Gladstone, two Home Rule Bills were introduced: one in 1886 which was defeated in the House of Commons, and another in 1893 which was defeated in the House of Lords. When the Third Home Rule Bill passed the House of Commons in 1912, the House of Lords no longer had the power to veto it completely, but rather to delay it for two years.

World War 1

The Home Rule Bill was set to become law in September 1914 when World War I broke out in Europe, and the implementation of Home Rule was shelved until the war ended, with a special provision for Ulster to be determined. The unexpected length of the war, coupled with events such as the Easter Rising during it, meant that the political context in Ireland was very different when the war ended in 1918 than when it began in 1914.