Ireland was neutral in WW2, however it was never invaded (by either side). How come? Why wasn't Ireland invaded by the UK to prevent the Germans invading? Why didn't germany invade ireland? It would have allowed them to open a new front for the British, or given a staging post to invade UK. Why didn't this happen?
Neither side really saw enough of a strategic advantage. The UK was already spread thin trying to defend their own island, so going out and trying to take control of Ireland didn't make sense, even if it meant preventing Germany from doing so. Given the long history of turmoil between England and Ireland, I believe they were content that Ireland didn't side with Germany.
As for the Germans, they were already fighting a war on two fronts. Once they took control of France, they had just as good a staging post as they would have had in Ireland (and maybe better). Also, Ireland would have been more difficult to defend and supply, whereas France was a lot easier on both accounts.
Neither the Germans nor the British were even remotely interested in what Ireland had to offer at the time. It was a neutral country tucked away in the NW corner of Europe. Its military was not particularly strong by any means, although the Irish Republican Party and Eamon de Valera had gained independence from the British largely by military force in the 20s.
To be more specific, the Germans were not interested in Ireland because:
the fledgling country did not pose a threat, militarily or politically or otherwise.
the Nazi ideology was not particularly opposed to the Irish people, many of whom were considered "Aryans",
invading and occupying would require a lot of naval/manpower for negligible gain,
the British would likely have helped defend it given its potential to stage a second attack front on Britain.
Furthermore, though Ireland was completely independent from Great Britain by 1939, there were still close ties between the countries and indeed many Irish soldiers were hired as mercenaries to fight for the British Empire -- on a volunteer basis. In this sense, they were unofficial allies of Great Britain. The enmity of the Irish Independence movement had certainly quieted by then.
All in all, you can think of it as a business decision if you will. The potential profit was very low, while the initial costs were very high. Britain couldn't care less about Ireland, unless it came to defending it, and Germany was much more focused on defeating the superpowers of the age: Britain, Russia, and later the United States.
Germany was not particularly capable of mounting an amphibious assault, especially to a destination on the opposite side of Britain.
The UK/America was not in the habit of invading neutral countries without justification. Doing so may have jeopardized their support from many other less powerful nations.
Also, Ireland didn't have much that was worth fighting for. The biggest advantage would have been shortening the Atlantic crossing, but that was hardly worth an invasion.
Both Germany and Great Britain had plans to invade Ireland.
Germany couldn't launch such an attack as they lacked the naval power to do it, as they knew that the Royal Navy would intervene. For the same reason they never tried to invade Great Britain, an invasion of Ireland would have been even more difficult due to the distances involved, they would have had few aircraft capable of operating at the distances required while the British would have been able to send forces from Wales and South West England for example.
Britain's plans to invade would be in response to any German invasion, so they were never required to actually invade.
There was a plan for an invited British invasion of Ireland IF the Germans invaded, called Plan W.
And although officially neutral Ireland did give some assistance to Britain in terms of allowing overflights by Atlantic patrol aircraft and returning British and allied aircraft and crew that were forced to make emergency landings.
Germany did in fact attempt to stir up unrest in Ireland, as seen by this BBC article: http://news.bbc.co.uk/1/hi/magazine/3264257.stm
The MI5 documents show that three men who landed on the southern coast of Ireland in 1940 were found with four bombs hidden inside cans labelled "French peas".
The saboteurs claimed they were for use against Buckingham Palace.
The three agents were landed by dinghy near Cork, but their exploits were shortlived.
Their tactic, of asking the first person they met if they could be taken to the IRA, did not work.
The man took them to the police instead.
The plot was dismissed as amateurish by MI5.
Unfortunately, the first Irishman they approached (whom they hoped would lead them to the IRA) handed them over to the police instead.
They also had plans of using the IRA as proxies/allies to invade Northern Ireland, but the plotters were also arrested.
So, they didn't get to invade Ireland, but not for lack of trying.
Ireland was a de facto ally of Britan. It had heavy trade ties with Britain and supplied it with volunteer soldiers and mercenaries. Irish industrial production came to Britain and ships under Irish flag transported British goods without a risk of being attacked. Conversely, forcing conscription of Irish population could lead to a pro-Germany unrest.
That said Britain was very much interested to have Ireland as a formally neutral country.
On the other hand, Germany simply had no means to attack Ireland because Britain had a strong fleet and any attack on Ireland was impossible without sea superiority.
If Hitler had conquered Great Britain, I think that they would have also invaded Ireland afterwards. Germany, despite its promises, did have plans to invade Switzerland and Sweden after defeating all other European countries, so I think Ireland would have suffered a similar fate. During the War, however, it simply did not have any importance or significance (exept for providing volenteer troops to Britain), so neither Hitler nor Britain would have bothered to attempt any kind of amphibious invasion.
Northern Ireland Prime Minister Lord Craigavon had asked Churchill in 1940 to invade the Republic of Ireland at the height of the war, as he felt that Valera was coming under the influence of Hitler.
Churchill did not move at that time but later prepared detailed plans for an invasion of southern Ireland.
Field Marshal Montgomery stated in his memoirs: “I was told to prepare plans for the seizure of Cork and Queenstown in southern Ireland so the harbors could be used as naval bases.”
Well, Germany was going to give aid to the Irish during the Easter Rebellion of 1916. They were not able to give them aid because of World War I raging on. Now for the British.. they were already still fighting the Irish in North and South Ireland, plus Ireland went through a civil war in the early 1920's so leadership was all jacked up. Eamon De'valara (Dev), also agreed somewhat with what Hitler was doing. NOT THE WHOLE HOLOCAUST PART, but after Hitlers death, Dev was quoted being upset with his death. Hope this helps :))