Reinforcements to the Royal Irish Constabulary recruited from British ex-soldiers and ex-sailors from January 1920. A shortage of RIC uniforms meant that new recruits were issued with khaki military trousers and dark green police tunics: this mixed dress gave rise to 'the Black and Tans'.
By permission of Oxford University Press
Connolly, S.J. (Ed.) The Oxford Companion to Irish History Oxford , O.U.P., 2nd Edition, 2002