The Irish War of Independence was a brutal and bloody affair , with violence and acts of extreme brutality on both sides . The British recruited hundreds of World War I veterans into the RIC and sent them to Ireland . Because there was initially a shortage of RIC uniforms , the veterans at first wore a combination of dark green RIC uniforms and khaki British Army uniforms , which inspired the nickname " Black and Tans " . The brutality of the Black and Tans is now well-known , although the greatest violence attributed to the Crown 's forces was often that of the Auxiliary Division of the Constabulary . One of the strongest critics of the Black and Tans was King George V who in May 1921 told Lady Margery Greenwood that " he hated the idea of the Black and Tans . " The most high-profile atrocity of the war took place in Dublin in November 1920 , and is still known as Bloody Sunday . In the early hours of the morning , Collins ' " Squad " killed fourteen British spies , some in front of their wives . In reprisal , that afternoon , British forces opened fire on a football crowd at Croke Park , killing 14 civilians . Towards the end of the day , two prominent Republicans and a friend of theirs were arrested and killed by Crown Forces
Bloody Sunday
Bloody Sunday (1920)
Irish Republican Army (1919–1922)