The armed Royal Irish Constabulary (RIC) was Ireland's major police force for most of the nineteenth and the early twentieth centuries. A separate civic police force, the unarmed Dublin Metropolitan Police controlled the capital. The cities of Derry and Belfast had special divisions within the RIC. The RIC was disbanded in 1922. It was replaced by two new police forces. The Garda Síochána (Guardians of the Peace) patrolled in the Irish Free State. The Royal Ulster Constabulary (renamed after the Good Friday Agreement the Police Service of Northern Ireland in 2001) patrolled the Northern Ireland state, which remained in the United Kingdom. The Dublin Metropolitan Police Force was disbanded in 1925, when it was incorporated into the Garda Síochána. About seventy-five percent of the RIC were Roman Catholic and about twenty five percent were of various Reformed Church persuasions, in line with Irish demographics. The RIC's successful system of policing influenced the Canadian North West Mounted Police, the Victoria Police force in Australia, and the Royal Newfoundland Constabulary in Newfoundland.

History of policing in Ireland:
The first organised police force in Ireland came about through The Peace Preservation Act of 1814. The Irish Constabulary Act of 1822 marked the beginning of the Irish Constabulary. The Act established a force in each barony with chief constables and inspectors general under the control of the UK civil administration for Ireland at Dublin Castle. By 1841 this force numbered over 8,600 men. The original force had been reorganised under The Act of 1836, and the first constabulary code of regulations was published in 1837. The discipline was tough and the pay was poor. The police faced continual civil unrest among the Irish rural poor, and was involved in many bloody confrontations during the period of the Tithe War. Other deployments were against organisations like the Ribbonmen, which attacked landlords and their property and stock.

The new constabulary first demonstrated its efficiency against civil agitation and Irish separatism during the Young Ireland campaign led by William Smith O'Brien in 1848. This was followed by a period of relative calm. The advent of the Irish Republican Brotherhood, founded in 1858, brought a plan for an armed uprising. Direct action began with the Fenian Rising of 1867. Fenians attacked on the more isolated police barracks and smaller stations. This rebellion was put down with ruthless efficiency. The police had infiltrated the Fenians with local informers. The loyalty of the Irish Constabulary during the outbreak was rewarded by Queen Victoria who granted the force the prefix 'Royal' and the right to use the insignia of the Most Illustrious Order of St Patrick in their motif. The RIC presided over a marked decline in general crime around the country. The unstable rural unrest of the early nineteenth century characterised by secret organizations and unlawful armed assembly was effectively controlled. Policing generally became a routine of controlling misdemeanours such as moonshine distilling, public drunkenness, minor theft, and wilful property crimes. A Land War broke out in the 1879-82 Depression period causing some general unrest. In Belfast, with its industrial boom, the working population mushroomed, growing fivefold in fifty years. There were serious riots in 1857, 1864, 1872 and 1886. As a result the small Belfast Town Police civic force was disbanded and responsibility for policing passed to the RIC.
From the 1850s the RIC performed a range of civil and local government duties together with their policing, integrating the constables with their local communities. By 1901 there were around 1,600 barracks and some 11,000 constables. The majority of constables in rural areas were drawn from the same social class, religion and general background as their neighbours. Strict measures were taken, however, to maintain an arms length relationship between police and public. A recruit was not permitted to serve in his home county or in the home county of his wife.

The task of enforcement of tens of thousands of eviction orders in rural Ireland caused the RIC widespread distrust among the Irish Catholic population during the mid nineteenth century. In the relative calm of the late Victorian and Edwardian periods, the RIC won general acceptance as an efficient and effective organisation which served as a model for similar forces elsewhere in the British Empire. It was no less popular at home than any other police force. The military ethos of the RIC, with its army terminology (the barracks, the carbines, and the emphasis on army style drill and smartness in dress) distinguished the force from civic police forces in the rest of the UK. The RIC wore a distinctive dark green uniform with black buttons and insignia, derived in style from the Rifle Brigade of the Armed Forces.

The RIC's existence was however increasingly troubled by the rise of the Home Rule campaign in the early twentieth century period prior to World War I. Sir Neville Chamberlain was appointed Inspector-General in 1900. His years in the RIC coincided with the rise of a number of political, cultural and sporting organizations with the common aim of asserting Ireland's separateness from England, which were often collectively referred to as Sinn Féin,. The potential success of the third Home Rule Bill in 1912 introduced serious tensions: opponents of the Bill organised the Ulster Volunteer Force in January 1913 while supporters formed the Irish Volunteers in response. These two groups had over 250,000 members, organized as effective private armies. In reports to the Chief Secretary for Ireland, Augustine Birrell, and the Under-Secretary, Sir Matthew Nathan, Chamberlain warned that the Irish Volunteers were preparing to stage an insurrection and proclaim Irish independence. However, in April 1916 when Nathan showed him a letter from the army commander in the south of Ireland telling of an expected landing of arms on the south-west coast and a rising planned for Easter, they were both 'doubtful whether there was any foundation for the rumour'. The Easter Rising began on Easter Monday, 24 April 1916 and lasted for six days, ending only when much of O'Connell Street had been destroyed by artillery fire. Although the Royal Commission on the 1916 Rebellion cleared the RIC of any blame for the Rising, Chamberlain had already resigned his post, along with Birrell and Nathan.

The Irish War of Independence:

The Sinn Féin victory in the general election of 1918 (the khaki election) was followed by the convention of an Irish Parliament (Dáil Éireann) at the Mansion House, Dublin. The announcement of a unilateral declaration of independence created a totally new political reality in Ireland.

On the day the new parliament first convened, January 21, 1919, two on duty RIC constables, Constable Patrick MacDonnell and Constable James O'Connell, were killed at Soloheadbeg, County Tipperary by an IRA raiding party while guarding dynamite in transit to the local mines. This marked the beginning of the Irish War of Independence. The Irish Republican Army under the leadership of Michael Collins began systematic attacks on UK government forces. While the Army controlled the cities, the RIC bore the brunt of these assaults in the provinces.

From Autumn 1919 onwards, the RIC was forced to abandon barracks in isolated areas. A national personal boycott of members of the force was declared by the IRA, alternative courts and an alternative enforcement units were set up. RIC members were threatened and some were assassinated. In October 1920, RIC wages were increased to compensate for increased hardship and cost of living increases. In rural parts, small shopkeepers often refused to serve the RIC fearing reprisals.

By October 1920, according to UK government sources, 117 RIC members had been killed and 185 wounded. Over a three month period during the same year 600 RIC men resigned from the force of 9,500. In the first quarter of 1920, 500 police barracks and huts in outlying areas were evacuated. The IRA had destroyed over 400 of these by the end of June to prevent their subsequent reuse.

The consequence of this was the removal of protection of persons and property in many outlying areas. As a result there was widespread intimidation, assault, murder and the wanton destruction of property. Large houses were burned, often to prevent use for policing or military purposes. Much of the country's rich architectural heritage was destroyed.

To reinforce the much reduced and demoralised police the United Kingdom government recruited returned World War I veterans from English and Scottish cities. They were sent to Ireland in 1920, to form a police reserve unit which became known as the "Black and Tans" and the Auxiliary Division of the Royal Irish Constabulary.

Paddy O'Shea, the son of a regular RIC sergeant, described these reinforcements as being "both a plague and a Godsend. They brought help but frightened even those they had come to help". Some regular RIC men resigned in protest at the often brutal and undisciplined behaviour of the new recruits.

Some RIC officers co-operated with the IRA, either out of political conviction, fear for their lives and welfare, or a combination of both. A raid on an RIC barracks in Cookstown, County Tyrone, in June 1920, was carried out with the help of sympathetic RIC men. The barracks in Schull, County Cork, was captured with similar inside aid. The IRA even had sympathisers within the upper echelon at Dublin Castle.

In December 1920, the Government of Ireland Act was proclaimed amid the fighting. The Parliament of Northern Ireland convened, and soon after decided to opt out of the new Irish state. After the Anglo-Irish Treaty was approved by Dáil Éireann, Irish Free State was formed in the south of the partitioned country. Northern Ireland remained in the UK. The Irish Free State became an independent Dominion within the Empire.

On 24 January 1922 Michael Collins won agreement in negotiation with the British Government for the dissolution of the RIC. Phased disbandments began within a few weeks with RIC personnel both regular and auxiliary being withdrawn to six centres in southern Ireland. On 2 April 1922 the force formally ceased to exist, although the actual process was not completed until August that year. The RIC was replaced by the Garda Síochána in the Irish Free State and by the Royal Ulster Constabulary in Northern Ireland.

Many RIC men went north to join the new RUC. This initially resulted in an RUC force that was over forty percent Roman Catholic at its inception.

Some RIC men joined the Garda Síochána. Many of these men had assisted the IRA operations in various ways. Some retired and the Irish Free State paid their pensions as provided in the terms of the Anglo-Irish Treaty agreement. Others, still faced with threats of violent reprisals, emigrated with their families to Britain or other parts of the Empire, most often to police forces in Canada, Australia, or New Zealand. A number of these men joined the Palestine Gendarmerie, which was recruiting in the UK at this time.