At that time in Dublin the inspector's uniform of Dublin's foot police circa 1833 with dress tunic and cap suggests a French influence, but which probably derived from the top hat of earlier years. With the crested helmet worn by by constables and sergeants of the same period, this head gear disappeared in the redesign of the DMP uniforms in 1900, to be replaced by the now familiar broad crowned forage cap. No example of the uniform depicted has survived

By 1900 the R.I.C. had about 11,000 men (70% of whom were Catholic) stationed in about 1,600 barracks. They were subjected to strict discipline with no official hours of duty or rest periods. Members could not serve in their native counties and had to have at least 7 years service before getting married. The intended wife had to be vetted by the superior officers before getting married. If permission to marry was obtained the couple were transferred to a county where neither had relatives.

The early years of the 20th century brought an array of elegant dress uniforms as Ireland played host to three British Monarchs. The illustration shows Inspector Chase of the Mounted Troop, D.M.P. wearing full dress, mounted order, circa 1914, wearing medals commemorating the Royal Visits to Ireland by Queens Victoria, King Edward VII and King George V. His medals from left to right - Queen Victoria's Medal to commemorate the Royal Visit, 1900; King Edward VII's Medal to commemorate the Royal Visit, 1903; and King George V's Medal to commemorate the Royal Visit 1911. By the turn of the century the duties of the Mounted Troop were largely ceremonial. In 1919 the Troop was abolished. Only one of the plumed helmets of the old horse police is known to have survived; it is in the Garda Síochána Museum. After Queen Victoria's death, the other members of the Mounted Troop wore a King's crown on their insignia; it is interesting to note that Inspector Chase continued to wear a Queen's crown on his helmet plate, collar, shoulder belt and sabretache. The Commissioner of the DMP in full dress ceremonial uniform. When the last Commissioner of the DMP under British rule, Lt Col Sir Walter Edgeworth Johnstone died in 1936, the Police College in Bramshill acquired his dress uniform. In 1963, this handsome reminder of a decorative period in Irish Police history was presented to the Garda Síochána and is now in the Garda Museum.

Officers of the DMP were required to appear in ordinary uniform when in charge of parties of police on inspection duty, and in the presence of the Viceroy on State occasion. They wore their dress uniforms on the direction of the Commissioner until 1919, when the Viceregal Commission under Justice Sir John Ross recommended "that full-dress uniform should no longer be required in either of the Irish Police Forces".

The early 1900's brought about a revival in Nationalism and Unionism with the creation of private armies such as the Ulster Volunteer Force, National Volunteers, Irish Volunteers and the Irish Citizens Army. The relative calm that the R.I.C. had experienced since the Land War of 1879-1882 was about to end. Following the executions of the leaders of the 1916 Easter Rising and the 1918 threat of conscription there was widespread civil unrest and resistance (both armed and passive) to British rule. Arthur Griffith's Sinn Féin won a landslide victory in 1918 and refused to take up their parliamentary seats in Westminster, instead the formed their own parliament in Dublin. On 21 January 1919, the same day that the members of the new parliament "Dáil Éireann" took its seats for the first time, an intensive guerrilla war was sparked off by the Soloheadbeg Ambush by the Irish Volunteers (later renamed the Irish Republican Army). During the next two years over 400 constables and nearly 150 soldiers were killed.

Attacks on the R.I.C. were widespread either in their barracks or while on patrol. Richard Bennett in his book "The Black and Tans" (London) 1959, p. 47, states that by the end of May 1920, 351 evacuated barracks were destroyed, 105 damaged, 15 occupied barracks were destroyed and 25 damaged, 19 Coastguard stations and lighthouses were raided for explosives and signalling equipment, 66 policemen and 5 soldiers were killed with 79 policemen and 2 soldiers wounded. DeValera and other members of the Sinn Féin government "Dáil Éireann", which claimed to be ruling Ireland in absentia, urged the shunning of the R.I.C. and their families by their neighbours and friends as agents of a foreign power. Widespread resignations from the R.I.C. followed.

Lloyd George's London Government created a temporary police force to supplement and assist the R.I.C. in their duties in the alarming situation, which was developing in Ireland. They were employed on a contract basis as Temporary Constables and recruited from unemployed rank and file World War One veterans. The recruits came from England, Scotland and Wales, with possibly a third of the new recruits from Ireland.

Shortly after their arrival in Ireland in March 1920, the Temporary Constables, whose duty was to hunt the IRA wore a dark bottle green and khaki uniform, were nicknamed the "Black and Tans" after a famous pack of hounds. Due to a shortage of R.I.C. dark bottle green uniforms that the Temporary Constables were dressed in a uniform, which was half black (the rifle green police) and half khaki (army).

In May 1920, Major General Sir Henry Hugh Tudor was appointed as police advisor to the Viceroy and commanding officer of both the Royal Irish Constabulary (R.I.C.) and the Dublin Metropolitan Police (D.M.P.). However, as the authorities tried to go on the offensive with the "Black and Tans" the R.I.C. resignations continued with over 500 resignations from the R.I.C. between 1 May 1920 and 31 July 1920. Resignations increased after the Listowel Police Mutiny of 17 June 1920 when the police stationed in Listowel R.I.C. Barrack's (now Listowel Garda Station) refused to hand over their barracks to the military.

Sinn Féin created its own Republican Police to supplant the R.I.C. In June 1920, the Irish Bulletin claimed that the Republican Police had arrested 84 criminals in 24 counties within 13 days. Three offenders who had been banished by a Republican Land Court to an Island off the west coast of Ireland for 3 weeks refused to be rescued by the R.I.C. saying that they were loyal citizens of the Irish Republic.

On 27 July 1920 a second temporary police force was recruited from unemployed W.W.I veterans who had been officers (with two exceptions) during the war. They were given the rank of Temporary Cadets. The Cadets who could wear either the R.I.C. uniform or army officers' uniforms with dark Glengarry caps and also employed on a contract basis. They became known as "The Auxiliaries" or "The Auxies" because they were sent as reinforcements to the R.I.C. and Temporary Constables. Together these new forces became known as "Tudor's Toughs" after their commanding officer.

Many of these new cadets had distinguished themselves on the battlefields of "The Great War". Two of whom, George Onions and James Leach, had been awarded the Victoria Cross for bravery during W.W.I. However, like the German soldiers of WW1 who were faced with similar warfare tactics after they had invaded Belgium, they were not trained in combating guerrilla warfare. Every civilian was a potential sniper and reprisals were widespread. The IRA's Flying Columns were active in nearly every part of the country. Tudor's Toughs who had been sent to Ireland as temporary police officers were now been accused of looting, arson and murder. Both sides engaged in bloody reprisals, the most notable was perhaps "Bloody Sunday," 21 November, 1920. After 11 English intelligence agents were assassinated and the Black and Tans fired upon unarmed spectators and players who were playing Gaelic football in Croke Park, Dublin, resulting in 12 dead and 60 wounded.

Peace eventually came with the Truce of July 1921 and the R.I.C. disbanded in the following year. A new police force "The Civic Guard" (renamed the "Garda Síochána na hÉireann" on 8 August 1923) was created by Michael Collins and the Irish Government. Many members of the R.I.C. joined the new force and some ended up as instructors to the new recruits and many of these new recruits were former members of the I.R.A. There was so much animosity towards the ex-R.I.C. officers that a group of recruits mutinied against their instructors, in what has become known as the Kildare Mutiny. After the mutiny the Civic Guard became an unarmed police force like their counterparts in the "Dublin Metropolitan Police". The D.M.P. and Garda Síochána were finally amalgamated in 1925.