In mid-1920 , republicans won control of most county councils , and British authority collapsed in most of the south and west , forcing the British government to introduce emergency powers . About 300 people had been killed by late 1920 , but the conflict escalated in November . On Bloody Sunday in Dublin , 21 November 1920 , fourteen British intelligence operatives were assassinated in the morning ; then in the afternoon the RIC opened fire on a crowd at a Gaelic football match , killing fourteen civilians and wounding 65 . A week later , seventeen Auxiliaries were killed by the IRA in the Kilmichael Ambush in County Cork . The British government declared martial law in much of southern Ireland . The centre of Cork city was burnt out by British forces in December 1920 . Violence continued to escalate over the next seven months , when 1,000 people were killed and 4,500 republicans were interned . Much of the fighting took place in Munster ( particularly County Cork ) , Dublin and Belfast , which together saw over 75 percent of the conflict deaths
Bloody Sunday
Bloody Sunday (1920)
Irish War of Independence