I think the most the EU could do is a mutual defence pact and one that would be far less robust than NATO, and perhaps a peacekeeping type operation.
You’ll never see an EU army. It’s just some federalist, militaristic fantasy, that you occasionally encounter in the Gaullist / centre right of France to project power, or in the U.K. tabloids who imagine the EU in 19th century Empire contexts because that’s the only model they understand, being Imperial fantasists.
It’s far from either of those fantasise and couldn’t operate like that. It doesn’t even like the concept of central executive power, let alone military power. It’s very much a Union based on friendly cooperation. Even leaving it in a huff resulted in a total anticlimax. You’ve tabloids jumping up and down with jingoism, while all the EU wants to do is have a boring divorce, and make sure Northern Ireland doesn’t spin into absolute chaos.
The EU is a lot more than French politics. Most of its members wouldn’t agree to something like an active military. It’s ethos is entirely about passivity and subsidiary, which means decisions are made at the most local level possible, and not centrally. You are also not going to see much of a desire to replace NATO.
The only context I could see that happening in would be if the US really went down a rabbit hole, went completely mad and became totally unhinged. For example if it turned into some kind of dystopian post Trump strongman authoritarian state, which isn’t impossible, but probably isn’t all that likely either.
Even in a scenario like that, I think it would be more likely that NATO would just end up winding back US heavy involvement and shifting to being a far more stand alone organisation. I mean Trump was keen to defund it anyway.
As for Ireland’s neutrality, a lot of that has to do with the timing of independence and the relationship with the U.K. in the 1930s. We were neutral, but pragmatically so and very much on the U.K., US and nowadays EU side of the argument.
For example, during WWII, if allied airmen landed in Ireland they were just quietly returned to the U.K., German airmen were held as POWs in the Curragh Camp until the end of the war. I’m actually aware of a story of a crew that deliberately ditched in Ireland to escape Germany and spent the war effectively interned, ended up staying and never went back to Germany after the war.
There was a lot of nod and wink type friendly arrangements with the U.K. and the allies and there were also the Treaty Ports that allowed Royal Navy presence in key ports during the war.
Like it or not, you have to remember Ireland fought a war of independence from Britain only 17 years before WWII began. There were *very+ bumpy relations with the U.K. in the 1920s and there was a legitimate concern that independence could have been lost again in a hypothetical “needs must” type scenario. That was the major reason for Irish formal neutrality, which wasn’t all that neutral at all in reality. There was also no way they were going to be putting the Irish army under the command of imperial forces either, given the very fresh history, but I suspect they would have been happy enough to work directly with the US.
If the Germans had invaded, I think you’d have been looking at Ireland more likely to side with and invited in the US and to have sought assurances or its independence. Remember that Irish-US relations run very deep. De Valera himself was an American btw. He was an Irish/Cuban New Yorker.
You’ve also various bilateral agreements with the US, and strange things like the US military use of Shannon to move troops, as long as they use the duty free…
There is also a formal agreement with the RAF which was entered into after the events of 9/11 and in a modern era of a far, far more positive relationship with the U.K. https://www.independent.ie/irish-news/secret-defence-pact-allowing-raf-jets-inirish-airspace-undermines-our-neutrality-says-td-berry-40526069.html
Even with Brexit chaos Irish-British relations run very deep and will continue to do so because of the realities of common interests, a lot of shared culture and geography. It’s not always going to be that we are on exactly the same page, but as relations go it’s close, warm and friendly, despite the history.
The WWII politics was far more complex and nuanced than people looking it in some kind of loyalty to the crown type view. We weren’t loyal to the crown at all nor are we very fond of crowns - that was the whole point. It doesn’t mean that we would have been unfriendly neighbours, nor does it mean we wouldn’t have been on the same side. After all the Irish / UK break up was one of the unusual situations where a democracy left a democracy and still maintained relations like a couple after an ugly divorce. There remains a lot of common ground and common interests.
Irish neutrality in the modern era morphed into more about being an ideology of non-militaristic peace. There is a lot of genuine concern about some of the less than purely defensive positions NATO has taken in various conflicts anytime Irish NATO membership is mentioned. It becomes a sticking point. We also have things like the “triple lock” which means Irish troops can only be sent abroad if the Government decides, the whole parliamentary system approves (and it’s much more diverse than Westminster due to PR voting) and if it’s authorised by the UN. We can’t legally act in any other circumstance.
Ireland has joined the EU prototype common defence programmes. It’s an active participant in UN peacekeeping, has worked in cooperation with NATO on peacekeeping and has a seat on the UN Security Council at the moment, but that’s about as far as it goes.
Our military expenditure is definitely far, far too small. Even for just practical safety it needs more resourcing and we aren’t lacking the wherewithal to do that. I can’t see Ireland having a need for huge spending, but we could definitely do with investing in strong passive defence: high tech primary radar, submarine detection etc and probably having the capability to intercept aircraft in much the same way as say Denmark or Norway - even if it’s solely for civil aviation protection reasons. We also need to be able to deal with cyber security threats and threats to infrastructure. We had a huge cyber attack on the health services in the middle of the pandemic. Admittedly, it was a bit of an open door but it does demonstrate the growing risks.
For a long time we’ve operated on the basis of “sure who’d ever want to invade us?” but we’ve grown into a small, but wealthy and more significant location with significant financial centre, a lot of strategic infrastructure for global IT, internet/telecoms, high tech manufacturing etc and one that is also a Eurozone and EU member. I think in a way we still imagine our strategic significance to be as irrelevant as it was in the 1950s but a lot has changed.
There is an active debate here about the realistic (or lack of realistic) approach to defence here and I think you will see some degree of movement towards beefing it up. I would have doubts that public support goes as far as NATO membership, and it’s likely such an issue would need a referendum make the necessary changes to the constitution to enter a military alliance. However, that’s also very much based on our current perception of not being under any external threat. Russia doing military tests off the coast and rumours of threats to cables was enough to trigger a lot of debate here.
At the end of the day, we’re an island and we are increasingly dependent on a lot of fibres, subsea power cables and gas lines. We need to be able to shore those up.