McCaughey's father was a founding member of the Irish Republican Dungannon Clubs and organized the first branch of Sinn Féin in Tyrone.
[2] As a teenager McCaughy joined the Gaelic League and Sinn Féin and also became a long time student and teacher of the Irish language.
[6][7] In September 1941 he was found guilty by a Dublin court of having detained and assaulted Stephen Hayes, IRA Chief of Staff who was accused of being a spy for the Irish Free State government.
Refusing to wear a criminal's prison clothes, he was kept in solitary confinement and spent nearly five years naked except for a blanket.
"[14][15] Sean McCaughey's funeral cortege passed through large crowds in the streets of Dublin and proceeded north to Belfast where it was met by thousands of mourners at Holy Cross Church, Ardoyne.