This chapter begins with an introduction to the prison system as it stood when the Free State government took over its administration in 1922. It then explores the use of detention during the Civil War period (1922 to c.1924), examining the development of the burgeoning system of incarceration arising out of the bitter, violent and divisive war following the signing of the Treaty with Britain on 6 December 1921. The Treaty concluded the War of Independence, which had been fought since 1919. The chapter details the reaction of prisoners to their incarceration and examines the nature of their resistance. It then goes on to describe prison policy as created by an independent Irish government, noting that prison policy was a marginal area of public policy, exciting little interest and engendering few innovations for many years. The nature of the Irish state and its governance is examined along with the social, economic, political and cultural influences on the prison system and its slow pace of development.