Ireland’s Wars: Operation Green

The Nazi conquest of the Low Countries and France brings us to a critical point of the Second World War. Much of Ireland’s strategic position at the outset of the conflict was based around the simple reality that it was too far away from Germany to be in serious danger of invasion, something banked upon by Britain to a lesser extent. The events of May and June in 1940 altered that paradigm hugely. Taking the north-western most portion of France, German forces could now claim to be less than 500 km’s of sea away from the Irish coastline. As plans progressed for a potential invasion of Britain, even as the RAF and Luftwaffe engaged in their critical battle in the skies, the thoughts of at least some in the German military now turned to Ireland as a possible target. The result of their thinking was Case Green, better known to history as Operation Green: the German plan for the military invasion of Ireland. And unlike the IRA equivalent in Plan Kathleen, Green was a very serious affair.

The exact genesis of Green is mired in a bit of a fog. We don’t know if there was a specific individual who drove the idea or was its main author, or which specific department of the German forces were responsible: Field Marshal Fedor von Bock, who had responsibility for the western flank of planned operations against Britain, is thought a possible candidate, though we know that the order to prepare implementation of the plan was issued to Leonhard Kaupisch, at the time a General of artillery in the Army Reserve, perhaps chosen for the task on the basis of his involvement in the occupation of Denmark. More than likely Green was initially conceived sometime in the first half of 1940 as part of speculative long-term planning, but it wasn’t until August of that year that something more concrete came together.

At that time the German military was preparing for the possible implementation of Operation Sea Lion, the amphibious invasion of Britain to follow in the wake of the intended destruction of the RAF. It was perhaps only natural that extensions of Sea Lion, or we might even call them side operations, were theorised. An attack on Ireland had some natural attractions for the Germans: a successful assault and occupation would tighten the strategic noose around Britain even more by allowing for the possibility of launching an invasion on the west side of the island, while any military operation in Ireland would necessitate a response from the British, forcing them to stretch their resources in defending a wider area than just their own territory. Of course there were some very obvious disadvantages, which I will discuss below. It is enough at this moment to state that German thoughts towards an attack on Ireland were understandable at that time, even if it probably did not occupy a huge amount of attention within German command structures.

Whoever was involved and however seriously the project was taken, Operation Green would end up containing within its pages a surprising amount of detail. Some of it was provided by information gathered by German agents over the previous few years, sometimes from tourist trips to Ireland, or from contacts among those German citizens living in Ireland. Other elements were taken from publicly available information, such as Ordnance Survey maps, or from German companies that had undertaken work in Ireland, like Siemens who had worked on the Ardnacrusha powerplant. The work was apparently completed in days, a sign of the level of competence within whatever department had been asked to draw it up. At the end of this process, a five volume work running to several hundred pages had been produced.

Given the short timeframe, the level of detail reproduced in Green was remarkable. The document contained information on Ireland’s historical background, geography, weather, industry, transport network, detailed maps and sketches of most significant urban areas, a lexicon of standard Irish phrases along with hundreds of photographs of areas deemed important, such as beaches and coastal towns. Later versions of the plan, when it was updated in 1941, would include details on tides, notable geological formations and suggested routes that German troops could take after the immediate landings on the coastline. Later still, aerial photography taken by Luftwaffe planes would add considerable more detail of sections of the Irish coastline. The document was not a flawless font of information though, with some details written down obsolete, such as the insistence that certain railway lines that had shut down were still operating. There was also an element of what we may call optimistic framing, with Ireland described as generally having an “excellent network of roads”, which in 1940 could only be considered, to put it mildly, as inaccurate.

The military purpose of Green was in conjunction with Sea Lion. German military forces were to attack Ireland with the aim of tying up British forces in Northern Ireland, denying the use of Ireland as a base for Britain and of using Ireland as a base from which to launch future attacks on the north of Britain. German soldiers – expected to to include artillery, commandos, anti-aircraft and bridge-building units alongside general infantry – were to embark from ports in the north-west of France and enact an amphibious landing on the south-east coast of Ireland, in a region between Wexford and Dungarvan. Upon establishing a beachhead – a task that was expected to be contested, with German landing craft instructed to prepare forward facing guns – reservists would take up the task of occupying captured territory as the rest of the Germans advanced inland to the point of Gorey in the east and Clonmel to the west. The initial landing force was pegged at just under 4’000 troops, but over 50’000 were expected to be involved in the overall operation. Other landing sites all along the coast of Ireland, from the Shannon estuary to Lough Foyle were also discussed, but the south-east was favoured.

Just what the Germans would do once they had advanced to the Gorey/Clonmel line is less clear: Green gets significantly less detailed at this point, and we can surmise that additional operations would have depended hugely on what was happening with Sea Lion. Success with that operation and it is reasonable to expect that the Germans would maintain their advance and militarily occupy the whole island. Defeat, and the possibility of a withdrawal would have been very real, even likely. We know that instructions to round up dissidents were included with the Green plans, and that Dublin was pegged as a future administrative centre of a German occupying authority between Britain and Ireland, but there are no other hints of what a German-occupied Ireland would have looked like.

How the IRA would have fitted into the whole affair is up for speculation. Their involvement is not part of Green, and their appears to have been no input from any Volunteers into the document. Either German planners felt they had enough detail already, or the IRA was not deemed credible enough to provide any worthwhile inclusions. Presumably if the German invasion plan had gone ahead the IRA would have been expected to fight on their side against the Irish state, but this probability was not factored in formally.

Could Greeen have worked? The answer is difficult to come too, as any success of the proposed operation would have depended heavily on what was happening with Sea Lion. There are many roadblocks that any German invasion force would have to either get past, or hope would be alleviated by fighting in the south of Britain. The naval contingent would have to get past the Royal Navy and the RAF, possible if they were tied up in the English Channel. The initial assault contingent would have to establish a beachhead, an extremely difficult task if such a landing was in any way contested: whatever the limitations of the Irish Defence Forces, if troops were able to assemble to oppose a landing they had many practical advantages, and the Germans would have needed a substantial air contingent to assist. As well, it must be remembered that the Germans may have had experience of modern warfighting from the campaigns in Poland, Norway, the Low Countries and France, but they had no experience of amphibious landings. If the Germans had established a beachhead, they presumably would then need to seize a port in order to get supplies, vehicles and more troops ashore; probably not unlikely if the beachhead was secure, though it would have to be done quickly. If all of these things were accomplished, an advance to the proposed Gorey/Clonmel line would certainly have been feasible, as the Irish military would have been ill-equipped to combat the Wehrmacht outside of opposing an amphibious landing. However, before the Germans would have gotten to that point, British military assets stationed in Northern Ireland would have advanced south, and others may have crossed the sea from the east. From there, it is the outcome of the Sea Lion that would have decided things.

At the heart of it all is the possibility that Green was never intended to be implemented, and instead was designed as a wartime ruse. Speaking after the war some German commanders would claim that the threat of invading Ireland was designed more to panic Britain and get London to alter its deployment of forces, and that an actual implementation of the plan was never a realistic possibility. Given the many difficulties inherent in Green, this is not the most far-fetched possibility. Sea Lion was already difficult enough, but a concurrent operation intended to be implemented over a wider area of sea must have seemed an impossibility to the men in charge of the Kriegsmarine.

In the end, it didn’t matter. The Germans would prove themselves unable to neutralise the RAF, and without air superiority over the Channel the idea of transporting troops to Britain, let alone Ireland, was simply too much of a risk. Sea Lion would be postponed in October 1940, and eventually abandoned as an idea altogether. Green thus became irrelevant to German war planning. Eventually copies of Green would make their way into the hands of British intelligence, who were all too happy to provide copies of the operation to their Irish counterparts, in the hope that knowledge of such things might at the very least forward the cause of Anglo-Irish military co-operation, if not push Ireland into becoming a belligerent.

The latter course was unlikely, especially at that time in 1942. By then the most dangerous moments had passed for Britain and Ireland. But the co-operation of elements of the British military and Irish Defence Forces was ongoing, and had been for some time. In the next entry we will discuss this co-operation, and the counter-measures to a scenario like Green that the two sides came up with.

To read the rest of the entries in this series, click here to go to the index.

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7 Responses to Ireland’s Wars: Operation Green

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