Complex sentence: The Curragh Camp was then the main base for the British Army in Ireland, which at the time formed part of the United Kingdom of Great Britain and Ireland, but was about to get a measure of devolved government, which included Ulster.
Split into simpler sentences: The Curragh Camp was then the main base for the British Army in Ireland, which at the time formed part of the United Kingdom of Great Britain and Ireland. Ireland was about to receive a measure of devolved government, which included Ulster.