An Irish republican and a volunteer in the Irish Republican Army, Behan was born in Dublin into a staunchly republican family becoming a member of the IRA's youth organisation Fianna Éireann at the age of fourteen. There was also a strong emphasis on Irish history and culture in the home, which meant he was steeped in literature and patriotic ballads from an early age. Behan eventually joined the IRA at sixteen, which led to his serving time in a borstal youth prison in the United Kingdom and he was also imprisoned in Ireland. During this time, he took it upon himself to study and he became a fluent speaker of the Irish language. Subsequently released from prison as part of a general amnesty given by the Fianna Fáil government in 1946, Behan moved between homes in Dublin, Kerry and Connemara, and also resided in Paris for a time.