Criminal Investigation Department (Ireland)

The unit had close links with the Army Intelligence and with a smaller "Protective Corps" which was based in the same building, Oriel House on Westland Row, Dublin.

Moynihan was given a temporary transfer from his post as Head of Military Intelligence and with the rank of Captain took over Oriel House for this new force.

On 22 August 1922 (the same day as Collins' death in an ambush), the Criminal Investigation Department was officially formed to "be distinct from existing police forces with separate headquarters under the direct control of the Minister for Home Affairs."

Broy, Nelligan and MacNamara, of the DMP "G" Branch, were there in the beginning, but all got high ranks in the National Army Intelligence Department and went instead to Wellington Barracks where their HQ was located[2] During the conflict of 1922–1923, the CID was responsible for the arrest of over 500 Anti-Treaty IRA fighters as well as the seizure of much weaponry and documentation.

There were many other such killings of Anti-Treaty activists by plain-clothed men in the Dublin area during the war, such as Bobby Bondfield in March 1923 and Noel Lemass in July of that year.

It is possible, however, that some of these killings were carried out by other agencies such as elements of the National Army, or by soldiers and CID men, but popularly attributed to "Oriel House".

A study of the period concluded, "Oriel House succeeded in its task of suppressing small-scale republican activities in the Dublin area, not by the sophistication and efficiency of its intelligence work ... but by the more direct method of striking terror into its opponents.