3 January – Tomás Óg Mac Curtain shot and mortally wounded Detective Garda SíochánaJohn Roche in Cork city centre. He had been disarmed by Garda Pat Malone in 1935. He was spared the death penalty in view of his father's history.
17 January – The Enid (Captain Wibe) of neutral Norway sailing from Steinkjer to Dublin, 10 miles north of Shetland, went to assist SS Polzella which had been torpedoed by German submarine U-25 which then shelled and sank Enid.
7 February – The Munster (Captain R. Paisley) was mined and sunk in the Irish Sea while entering Liverpool.[1]
The British Cato (Captain Richard Martin) sailing from Dublin to Bristol, struck a mine 2½ miles west of Nash Point: 13 died, 2 survived.
9 March – The trawler Leukos was sunk by gunfire from German submarine U-38, northwest of Tory Island – 11 died.[1] (She may have moved between the surfacing U-boat and English trawlers, in the hope that the Irish tricolour would protect her while the English escaped.)
10 March – The City of Bremen rescued 33 crew of the Amor (Dutch) in the North Sea.
20–24 April – Plan Kathleen, an Irish Republican Army (IRA) plan for a Nazi German invasion of Northern Ireland, was presented to the Abwehr (German military-intelligence service).[2]
April – Two men died on hunger strike for political status in Mountjoy Jail, Dublin.[3]
24 May – The first secret meeting to formulate 'Plan W' – joint action in the event of a Nazi invasion of Ireland – was held between Irish officials and the British military in London.
The Uruguay of neutral Argentina, sailing from Rosario to Limerick with 6,000 tons of maize, sank with scuttling charges by German submarine U-37 160 miles from Cape Villano: 15 died, 13 survived.
10 June – The Violando N Goulandris of neutral (at this time) Greece sailing from Santa Fe, Argentina to Waterford with a cargo of wheat was torpedoed by German submarine U-48 off Cape Finisterre: 6 died, 22 survived.
12 June – German submarine U-38 landed a German spy, Karl Simon, in Dingle. He was promptly arrested and interned for the duration of the war.
4 July – Taoiseach Éamon de Valera announced that the policy of neutrality adopted the previous September would not be reversed.
7 July – Operation Lobster I: Three German agents were infiltrated into Ireland.
11 July – The Moyalla rescued twenty survivors from the British Athellaird off Cape Clear Island.
15 July
The City of Limerick (Captain R. Ferguson) was bombed by aircraft and sank in the Bay of Biscay, 700 miles west of Ushant – two died.[1]
Republican Frank Ryan was released by the authorities of Francoist Spain from Burgos prison into the hands of the German Abwehr.
20 July – The City of Waterford (Captain T. Freehill) was shelled by submarine in North Atlantic, but escaped.
30 July – The Kyleclare rescued 52 survivors from the British Clan Menzies off the County Mayo coast.
1 August – The collier Kerry Head was bombed off Kinsale; she survived this attack (but see 22 October).
8 August
Operation Dove: Republicans Seán Russell and Frank Ryan embarked from Nazi Germany on German submarine U-65 for infiltration into Ireland, but Russell fell ill and died on the passage, and the operation was abandoned.
15 August – The Meath (Captain T. MacFariane) was mined and sunk off the South Stack, Holy Island, Anglesey;[1] the crew was rescued by a local fishing trawler but 700 cattle were lost.
16 August – The Loch Ryan (Captain J. Nolan) was bombed off Land's End, but survived.[1]
24 August – The City of Waterford (Captain T. Freehill) was bombed in Irish Sea but survived.
26 August – Five German bombs were dropped on County Wexford in a daylight raid. One hit the Shelbourne Co-operative Creamery in Campile, killing three women.[6]
27 August – The Lanahrone rescued 18 survivors from the British Goathland off the County Kerry coast.
4 September
The Luimneach (Captain E. Jones) was sunk by gunfire from German submarine U-46 in the Bay of Biscay.[1]
The Edenvale (Captain N. Gillespie) was machine-gunned by German plane off Waterford coast.[1]
27 September – The Manchester Brigade was torpedoed off the Aran Islands.
3 October – The German news agency announced that the German government was willing to pay compensation for dropping bombs on Dublin.[7]
22 October – The Kerry Head (Captain C. Drummond) was bombed again: all twelve hands were lost, in full view of watchers on Cape Clear Island.[1]
26–28 October – RMS Empress of Britain, serving as a troopship under the British flag, was bombed, torpedoed and sunk off the Donegal coast with the loss of 45 lives. At 42,348 GRT she was the war's largest merchant ship loss.
7 November – Éamon de Valera, speaking in response to Winston Churchill's statement, said that there could be no question of handing over Irish ports for use by British forces while Britain retained control of Northern Ireland.
11 November – The Ardmore (Captain T. Ford) struck a mine off the Saltee Islands – 24 died.
19 December – Lightship tender Isolda (Captain A. Bestic) was sunk by German bombers within sight of Carnsore Point: six were killed, seven wounded.[1]
4 October – Brian O'Nolan's first "Cruiskeen Lawn" humorous column was published in The Irish Times; from the second column he used the pseudonym 'Myles na gCopaleen'. The original columns were composed in Irish. He continued writing the column until his death in 1966.
October – The Bell, a liberal monthly magazine of literature and social comment, was established in Dublin by Peadar O'Donnell under the editorship of Seán Ó Faoláin.
Seán Ó Faoláin published his travelogue An Irish Journey and novel Come Back to Erin.
^ abcdefghijForde, Frank (2000). "Appendix 3: Beligerent Action against Irish Ships". The Long Watch: World War Two and the Irish Mercantile Marine (rev ed.). Dublin: New Island. ISBN1-902602-42-0.
^Hull, Mark M. (2002). Irish Secrets. German Espionage in Ireland 1939–1945. Dublin: Irish Academic Press. ISBN0-7165-2756-1.
^Wills, Clair (2007). That Neutral Island. London: Faber. ISBN9780571221059.
^Militärgeographische Angaben über Irland. Berlin: Generalstab des Heeres, Abt. für Kriegskarten und Vermessungswesen (IV. Mil.-Geo.), 1940. OCLC 10934333.
^"Three Irish Girls Killed By German Bombs". The Irish Times. 27 August 1940.
^"German Compensation for Bombing at Campile". The Irish Times. 14 February 1946.
^Bourke, Marcus (1993). Murder at Marlhill: Was Harry Gleeson innocent?. Dublin: Geography Publications. ISBN0-906602-23-8.
^"Bombs Fall in County Dublin". The Irish Times. 21 December 1940.