[2] A small IRA battalion existed in Derry since the Troubles began,[citation needed] but it never had a steady number of volunteers until Bloody Sunday, which saw an influx of new recruits.
The highest position was occupied by the Brigade's officer commanding, the top IRA ranking in the city.
Beneath him was the ten-men Derry Brigade Command, made of experienced IRA volunteers, among them one or two prominent Sinn Féin politicians.
The lower layer was the Command Staff, which includes the quarter-master, the engineering department, the financial department and internal affairs, the latter to deal with informers.
[1] The Command Staff, through their Officer Commanders, operated active service units in the four republican strongholds of the city: Bogside/Brandywell district, Creggan, Waterside and Shantallow.