Irish War of Independence: British police known as "Black and Tans" burn the town of Balbriggan and kill two local men in revenge for an IRA assassination.

The Irish War of Independence, also known as the Anglo-Irish War, was a guerrilla war fought in Ireland from 1919 to 1921 between the Irish Republican Army and British forces: the British Army, along with the quasi-military Royal Irish Constabulary (RIC) and its paramilitary forces the Auxiliaries and Ulster Special Constabulary (USC). It was part of the Irish revolutionary period.

The Black and Tans were constables recruited into the Royal Irish Constabulary (RIC) as reinforcements during the Irish War of Independence. Recruitment began in Great Britain in January 1920, and about 10,000 men enlisted during the conflict. The majority were unemployed former British soldiers from England, Scotland, and Wales who had fought in the First World War. Some sources count Irish recruits to the RIC from 1920 as "Black and Tans".

The sack of Balbriggan took place on the night of 20 September 1920, during the Irish War of Independence. Auxiliary members of the Royal Irish Constabulary known as "Black and Tans" went on a rampage in the small town of Balbriggan, County Dublin, burning more than fifty homes and businesses, looting, and killing two local men. Many locals were left jobless and homeless. The attack was claimed to be revenge for the shooting of two police officers in Balbriggan by the Irish Republican Army (IRA). It was the first major 'reprisal' attack against an Irish town during the conflict. The sack of Balbriggan drew international attention, leading to heated debate in the British parliament and criticism of British government policy in Ireland.

The Irish Republican Army was an Irish republican revolutionary paramilitary organisation who waged a guerrilla campaign against the British occupation of Ireland in the 1919–1921 Irish War of Independence. It was descended from the Irish Volunteers, an organisation established on 25 November 1913 that staged the Easter Rising in April 1916. In 1919, the Irish Republic that had been proclaimed during the Easter Rising was formally established by an elected assembly, and the Irish Volunteers were recognised by Dáil Éireann as its legitimate army.