Ireland did not brake away from Great Britain, the republic of Ireland has its own government, six counties in the North remained loyal to Great Britain, which then became the United Kingdom of Great Britain and Northern Ireland.
Ireland has a long history of uprisings and civil wars from days of Henry II till the separation in 1922. Catholic and Protestant differences, settler and local differences, Scottish settlements, Penal Code RC having no right of offices or possession of land for locals and other policy failures brought many civil wars.
In 1914, a measure of home rule was granted but outbreak of war prevented its operation. In1921, Sinn Fein party set up Irish republic and countries those refused to separate were formed a separate state as Northern Ireland under U.K.