As Adjutant of D Company, 2nd Battalion of the Dublin section of the Volunteers he fought in the Jacob's Factory Garrison during the Easter Rising of 1916 under Thomas MacDonagh.

He was arrested on one occasion in 1920 during a strike for better conditions for members of his union and was imprisoned in Mountjoy for two weeks when he refused to take bail as he said he had done no wrong.

[citation needed] During the Bloody Sunday action to wipe out a group of Dublin -based British spymasters known as the Cairo Gang, on 21 November 1920, Moran headed the IRA squad that killed two men in the Gresham Hotel in O'Connell Street: Leonard Wilde, a former British Consul in Spain,[4] and Patrick Joseph MacCormack, a World War I veteran and ex-jockey.

MacCormack's mother, Kate, a veteran of the Land War and relative of Michael Davitt who lived in Dun Laoghaire, mounted a vigorous campaign to clear her son's name of what she saw as the taint of being a British spy.

[5] While in detention at Arbour Hill Prison, Moran was subjected to a number of identity parades and identified as being the man who had held up a motor cyclist outside 38 Mount Street, Dublin where Lt. Peter Ashmun Ames, an American-born British military intelligence officer, was murdered (21 November 1920).

However, Moran refused to take the opportunity to escape as he reportedly felt the authorities would interpret it as an admission of guilt, telling O'Malley "I don't want to let down the witnesses who gave evidence for me.

[9] The Irish National Union of Vintners' Grocers' & Allied Trades' Assistants, of which Moran had been an active member, called a half-day general strike on the morning of the executions and over 40,000 people gathered outside Mountjoy to pray for the six men who were hanged between 6am and 8pm.

The townships of Bray, Dún Laoghaire, and Blackrock closed down, with the municipal flags flying at half-mast, on the day of his hanging, with Mass celebrated in all churches every hour from 6am to noon.