The Anglo-Irish Treaty, 1921

The Anglo-Irish Treaty, signed on 6 December 1921, took effect exactly a year later on 6 December 1922. The Irish Free State – a new Dominion within what was then the British Empire – was born.

Negotiations between the UK Government and representatives of Sinn Féin had begun on 11 October 1921 in an attempt to answer what was known as the “Irish Question” once and for all. The talks followed decades of attempts by the UK Parliament to give a degree of autonomy known as “Home Rule” to Ireland.

The resulting Anglo-Irish Treaty gave 26 counties of Ireland a parliament (the Oireachtas) with jurisdiction over most domestic affairs, significant fiscal autonomy and a military force (although the UK was to retain temporary control of several military ports). The Treaty also kept the Irish Free State firmly under the Crown. A Governor-General was to represent the monarch, while members of the Dáil Éireann (lower house) and Seanad Éireann (upper house) were required to swear an oath of fidelity to the Crown.

The Treaty did not create “partition” but granted the Parliament of Northern Ireland the option of joining the Free State after a period of one month or remaining a devolved part of the United Kingdom. It chose the latter, which, under the terms of the Treaty, triggered the formation of a Boundary Commission charged with revising the boundary between the two parts of Ireland.

Lord Birkenhead, the then Lord Chancellor and one of the UK negotiators in 1921, described the Treaty as “a document which, I believe, will be memorable in history”.

This research paper first examines the historical background to the negotiations that led to the Treaty. It then examines each clause before considering how the Treaty was given the force of law in the UK and Ireland. Finally, it examines changes to the Treaty which occurred during the 1930s.