To date, Ireland has not sought to become a member of NATO due to its traditional policy of military neutrality. Its constitution stated, "Save in the case of actual invasion, the Irish Free State Many countries made neutrality declarations during World War II.
However, Ireland which refers to the period as the emergency was one of a handful of European states to remain neutral to the end of the war. The Irish government had good reason to be concerned that supporting either side in the conflict could reignite grievances of the Irish Civil War , as there were pro- and anti-fascist movements in Ireland.
The possibility that the Irish Republican Army might link up with German agents in line with the Irish republican tradition of courting allies in Europe against the colonial power of the UK to secure their full independence , and thereby compromising Irish non-involvement, was considered. Additionally, there were fears that the United Kingdom, eager to secure Irish ports for their air and naval forces, might use the attacks as a pretext for an invasion of Ireland.
It was believed that Ireland would take the German side if the United Kingdom attempted to invade Ireland, but would take the British side if invaded by Nazi Germany. In , British envoy Malcolm MacDonald proposed an end to the partition of Ireland and acceptance of "the principle of a United Ireland" if the independent Irish state abandoned its neutrality and immediately joined the war against Germany and Italy.
Ireland's fulfillment to the letter of the rules of neutrality has been questioned. Ireland supplied important secret intelligence to the Allies , for instance, the date of D-Day was decided on the basis of incoming Atlantic weather information , some of it supplied by Ireland but kept from Germany. Ireland also secretly allowed Allied aircraft to use the Donegal Corridor , making it possible for British planes to attack German U-boats in the mid-Atlantic.
