History records that Ireland has long occupied a place in the strategic military planning of other nations, writes Dr David Murphy of the Department of History.

    Ireland has featured in the strategic military planning of many nations throughout the centuries. This was often in the context of another power's conflict with Britain and included their intention of co-operating with Irish forces on arrival. Spain and France are prominent in Irish history and cultural memory for their military expeditions to Ireland, but plans to invade Ireland can also be found in military archives in Germany, Britain, the United States and elsewhere.

    As a nation, we have assumed we existed in a benign strategic environment for many decades, but this sense of security has been challenged in recent years in the context of a worsening global security situation. Processes of globalisation have brought Ireland very much into the wider strategic picture and we have yet to grasp the implication of that as a society in many ways.

    But Ireland’s place in the wider strategic planning of other powers is nothing new. A common theme in historic invasion plans has been the tendency of European powers to factor Ireland into their war plans against Britain. If sending an invasion force to Ireland assisted a local rebellion, that was an added bonus.

    In the years running up to the Armada campaign, Philip II of Spain developed several strategic scenarios that included Ireland and he even sponsored a small and unsuccessful expedition to Ireland in 1580. In Philip II’s grand strategy, he saw the possession of Ireland as the basis for a subsequent invasion of Britain from the west, perhaps in conjunction with a further Spanish force crossing the sea from Flanders.

    Following the failure of the Armada plan of 1588, Ireland featured more significantly in Philip’s strategic planning up until his death in 1598. His successor, Philip III, sent a Spanish force to assist Irish forces during the Kinsale campaign in 1601.

    France also fought a succession of wars with Britian up to the early 19th century. It is not surprising therefore, to find a collection of invasion planes at the Service Historique de la Défense (French military archives) at Vincennes. These included plans to assist Jacobite forces in Ireland in the early 1690s, plans to land the Young Pretender, Charles Edward Stuart ("Bonnie Prince Charlie"), in Ireland in the 1740s and 1750s and obviously plans for General Hoche's failed expedition of 1796.

    The expedition of General Humbert to Ireland in 1798 was the most impactful, both militarily and in the context of Irish cultural memory. The last set of French plans for an invasion of Ireland were developed surprisingly late, between 1900 and 1904, before the emerging German threat led to the Entente Cordiale between Britain and France.

    From a German perspective during the First World War, Sir Roger Casement endeavoured to enlist German support for an Irish rebellion. In 1916, this extended to providing a U-boat to land Casement back in Ireland, sending a ship of captured Russian weapons (the Aud) and increased German naval activity off the east coast of Britain. These were not insignificant efforts but a full invasion of Ireland was never on the cards for Germany during WWI.

    In the mid-1930s, German attention turned to Ireland again and it is obvious from the records that survive that German tourists and students were gathering intelligence on Irish ports, roads, and rail networks during trips to Ireland before WWII. This material would eventually come together in Plan Green (Fall Grün), the German plan to invade Ireland, which was developed during the summer of 1940.

    This plan envisaged a German amphibious landing on the Wexford coast, which would be followed by a push towards Dublin. A crucial requirement of this plan was the implementation of Operation Sealion, the German plan to invade Britain. Germany’s failure to gain air dominance during the Battle of Britain meant that Sealion was cancelled, as was Plan Green. The Germans developed some further plans for Ireland during WWII, none of which got beyond the early planning phases.

    In the context of WWII, the Treaty Ports, which had only been handed back to the Irish state in 1938, were a key factor for Britain. Winston Churchill requested the development of a plan to retake these strategic ports and even had a commander in mind for the operation, namely General (later Field-Marshal) Sir Bernard 'Monty' Montgomery, who had served in Ireland during the War of Independence and who later had a significant WWII career.

    Ultimately, Irish and British military planners would co-operate in the development of Plan W, a plan for the joint defence of the island of Ireland by both British and Irish forces. A copy of the German Plan Green and copies of the Irish Army’s defence plans are held in the Military Archives in Cathal Brugha Barracks, Dublin.

    It is perhaps surprising to note that the United States had developed a plan to invade Ireland as part of the "Rainbow" operational plans developed throughout the 1920s and 1930s. This strategic planning process outlined various contingencies and developed a series of colour-coded plans, focusing on different countries and possible scenarios.

    Plan Red envisaged a war between the US and Britain and, within this potential scenario, Plan Emerald was developed as an intervention in Ireland. These plans were recast in the context of the worsening international situation in the late 1930s and Plan Emerald was redeveloped as a potential reaction to a German invasion of Ireland.

    In the Cold War period, Ireland still featured in the strategic planning of various nations. Russian military maps for Ireland survive and one must assume that NATO states developed their own reaction plans. As more records are released, new research will no doubt shed new light on these plans.

    In recent years, I have introduced a wargame exercise in Maynooth University's MA in Military History & Strategic Studies, that is based on the German Plan Green. It raises some interesting points. In the context of the wargame, Operation Sealion is underway and no help is available from outside Ireland. The Irish team is equipped with more men and equipment than were available to the Irish Army in 1940, yet still that team has lost every iteration of the exercise. It shows that even a small island is difficult to defend with limited resources.

    It is instructive too in terms of "lessons learned" for the current Irish defence environment. A surprising factor of the wargame has been the willingness of Irish teams to switch to the German side as the "invasion" scenario developed. This very much reflects some behaviours in occupied countries during the 1940s, but also suggests a lack of modern awareness of the realities of Nazism.

    History would suggest that an invasion of Ireland has consistently featured as part of wider strategic plans against Britain and, in the Cold War context, against NATO. If plans to invade Ireland have been developed by various powers over the centuries in pursuit of their own strategies, it is likely that we remain on the global strategic radar in the current context.

    This piece originally appeared on RTÉ Brainstorm