In January 1939, the IRA Army Council declared war against Britain, and the Sabotage Campaign began a few days later.
The so-called "S-Plan" saw IRA operatives based in Britain bombing British infrastructure, with a view to weakening their war effort.

On 23 December 1939, IRA members stole almost the entire reserve ammunition store of the Irish Army from the Magazine Fort in Dublin's Phoenix Park.
This became known as the "Christmas Raid" in IRA folklore.
The Royal Ulster Constabulary (RUC) found two and a half tons of the stolen ammunition inside County Armagh on 2 January 1940.
The next day the Irish Minister for Justice, Gerald Boland, at an emergency session of the Dáil, introduced the Emergency Powers Bill to reinstate internment, Military Tribunal, and executions for IRA members.
It was rushed through and given its third reading the next day creating the Emergency Powers Act.
It was later used to execute at least six IRA volunteers in Ireland between 1940 and 1944.
Peter Barnes and James McCormack who had been arrested in England shortly following an IRA bomb that exploded in Coventry on 25 August 1939 resulting in the deaths of several uninvolved English civilians, were executed on 7 February 1940.
Republican publication An Phoblacht did not deny their mission in England and IRA membership but maintains that they were not involved with the Coventry bombing.

By 1941, the IRA numbered fewer than 1,000 members, many of whom were imprisoned.
Most of its able political organisers had left in the mid- to late-1930s and its "natural constituency" had been appropriated by Fianna Fáil.

During the Second World War, the IRA hoped for support from Germany to strike against Britain.
Seán Russell travelled to Germany in 1940 to canvass for arms.
He became ill and died on board a German U-boat which was bringing him back to Ireland in August that year along with Frank Ryan (see Operation Dove).
Stephen Hayes, the acting Chief of Staff, prepared an invasion plan for Northern Ireland and sent it to German Intelligence in 1940; this plan was later called Plan Kathleen, but it was discovered by the Irish authorities within one month of its creation.
The Irish Government opposed the IRA's collaboration with Nazi Germany, having adopted a position of neutrality.

Gunther Schuetz, a member of the Abwehr (German military intelligence), parachuted into Ireland and was almost immediately arrested.
On 28 February 1942 he escaped.
The IRA intended to send him back to Germany with a request for weapons, ammunition, explosives, radio equipment and money.
The IRA Army Executive met on 20 April and sanctioned the request.
They also approved a plan to "give military information to powers at war with England even before any definite contacts [were] established with these powers", provided the information did not endanger civilians.
The plan was quickly discovered when an IRA courier was arrested on the Dublin-Belfast train with documentation of the decisions taken, and details of the Nazi contact.
This led to the arrest of Schuetz, on 30 April, only hours before he was due to set sail.
The boat was seized and the crew arrested.

In Belfast, much to the alarm of the Northern Ireland authorities, the city's brigade had developed a "Protestant squad", an intelligence unit, largely recruited by John Graham, a Church of Ireland devout, from Denis Ireland's Ulster Union Club.
But while Graham, who opposed cooperation with the Germans, and others in the Belfast command continued to debate the merits of a new northern campaign, in April 1942 a diversionary action, intended to draw the RUC from an illegal 1916 commemoration, developed into a street gun battle.
A police constable, father of four Thomas James Forbes, was killed, in consequence of which six of the eight members of the active unit were sentenced to death.
In the event all but one were reprieved.
On 2 September 1942 Tom Williams, nineteen, was hanged the first, and only, Irish Republican to be judicially executed in the North.
 
It has been rumoured that during the war period IRA members may hav
In January 1939, the IRA Army Council declared war against Britain, and the Sabotage Campaign began a few days later. The so-called "S-Plan" saw IRA operatives based in Britain bombing British infrastructure, with a view to weakening their war effort.
On 23 December 1939, IRA members stole almost the entire reserve ammunition store of the Irish Army from the Magazine Fort in Dublin's Phoenix Park. This became known as the "Christmas Raid" in IRA folklore. The Royal Ulster Constabulary (RUC) found two and a half tons of the stolen ammunition inside County Armagh on 2 January 1940. The next day the Irish Minister for Justice, Gerald Boland, at an emergency session of the Dáil, introduced the Emergency Powers Bill to reinstate internment, Military Tribunal, and executions for IRA members. It was rushed through and given its third reading the next day creating the Emergency Powers Act. It was later used to execute at least six IRA volunteers in Ireland between 1940 and 1944. Peter Barnes and James McCormack who had been arrested in England shortly following an IRA bomb that exploded in Coventry on 25 August 1939 resulting in the deaths of several uninvolved English civilians, were executed on 7 February 1940. Republican publication An Phoblacht did not deny their mission in England and IRA membership but maintains that they were not involved with the Coventry bombing.
By 1941, the IRA numbered fewer than 1,000 members, many of whom were imprisoned. Most of its able political organisers had left in the mid- to late-1930s and its "natural constituency" had been appropriated by Fianna Fáil.
During the Second World War, the IRA hoped for support from Germany to strike against Britain. Seán Russell travelled to Germany in 1940 to canvass for arms. He became ill and died on board a German U-boat which was bringing him back to Ireland in August that year along with Frank Ryan (see Operation Dove). Stephen Hayes, the acting Chief of Staff, prepared an invasion plan for Northern Ireland and sent it to German Intelligence in 1940; this plan was later called Plan Kathleen, but it was discovered by the Irish authorities within one month of its creation. The Irish Government opposed the IRA's collaboration with Nazi Germany, having adopted a position of neutrality.
Gunther Schuetz, a member of the Abwehr (German military intelligence), parachuted into Ireland and was almost immediately arrested. On 28 February 1942 he escaped. The IRA intended to send him back to Germany with a request for weapons, ammunition, explosives, radio equipment and money. The IRA Army Executive met on 20 April and sanctioned the request. They also approved a plan to "give military information to powers at war with England even before any definite contacts [were] established with these powers", provided the information did not endanger civilians. The plan was quickly discovered when an IRA courier was arrested on the Dublin-Belfast train with documentation of the decisions taken, and details of the Nazi contact. This led to the arrest of Schuetz, on 30 April, only hours before he was due to set sail. The boat was seized and the crew arrested.
In Belfast, much to the alarm of the Northern Ireland authorities, the city's brigade had developed a "Protestant squad", an intelligence unit, largely recruited by John Graham, a Church of Ireland devout, from Denis Ireland's Ulster Union Club. But while Graham, who opposed cooperation with the Germans, and others in the Belfast command continued to debate the merits of a new northern campaign, in April 1942 a diversionary action, intended to draw the RUC from an illegal 1916 commemoration, developed into a street gun battle. A police constable, father of four Thomas James Forbes, was killed, in consequence of which six of the eight members of the active unit were sentenced to death. In the event all but one were reprieved. On 2 September 1942 Tom Williams, nineteen, was hanged the first, and only, Irish Republican to be judicially executed in the North.  
It has been rumoured that during the war period IRA members may hav
Irish Republican Army (1922–1969)