Are there armies in any time in history in which individuals should have served in the military to do the most good in expected global utility? If so, what seems to be the criteria?
Arguably the codebreakers at Bletchley Park during WWII were doing a tremendous amount of good that they wouldn't have been able to match doing other things. But in the context of conscription, this kind of thing seems extremely unlikely. Not only does it depend on a comically evil yet powerful enemy, it also depends on the ability of a handful of individuals to make an outsized contribution to the war effort by means of their scarce, special skills. There does not seem to be anything half as dangerous as Nazi Germany that we can fight by military means, and it is not clear that there is a comparable niche in which people with special skills can do much good in. Of course, even if there were such a niche, chances are you would not have the ability to exploit it, almost by definition.
I suspect that for the typical person in the developed world, working their usual job and donating any surplus income to effective charities vastly outweighs the marginal good they would do joining any military in any capacity. So I believe that the answer to your last question is Yes, you should expect a random EA to regret joining the military (assuming that the only thing that motivates them is EA concerns). And I believe that the factors in favour of not joining are so overwhelming that the answers to your second and third questions, no matter what they may be, would not change the calculus.
So if we assume that the person is in such a niche, and has the ability to exploit it, then the question would be to quantify how evil is the enemy. Israel's favorite enemy these days is Iran, so it seems that I should learn more about Iran and give my best predictions regarding it's future. One thing that immediatly comes to mind is that there are many similarities between Saudi-Arabia and Iran, while Israel seems to have a good relationship with Saudi-Arabia, so on what grounds should I believe that Iran is evil?
A large part of why the code breakers produced so much value was that there was an open war and ending open wars is high utility. Given that there's no open war between Israel and Iran it's unlikely that you would get similar gains even if you think Iran is evil (whatever a country being evil is supposed to mean).
From an EA perspective the core issue with engaging personally with the military is marginal impact. Most miltiaries engage in a lot of immoral actions in which they don't really have to engage to achieve their goals. Scandals like Abu Graib happen because people in the military aren't making calculated utilitarian decisions.
If you have the psychlogical profile where you think you can push decision inside the military where you are involved into the right direction the resulting impact of that shift is likely a lot higher than the resulting marginal impact of your fighting power.
First, the fact that others have declared it "mandatory" doesn't exempt you from moral choices. There are always options. Second, there are a lot of different ways one might answer those questions. You don't define what "good" is (maximize conscious population? Maximize average or peak satisfaction? Improve standing of one culture, even if an opposing culture has more members? Whatever your metric, do you maximize a point-in-time or integrate over some timespan?), and this is necessary to guide your decisions.
One possible framing for these questions:
Are there armies in any time in history in which individuals should have served in the military to do the most good inexpected global utility? If so, what seems to be the criteria?
I'd argue that most members of the winning side in a fight believe they did the best thing by fighting. If you think technological progress and higher density of humans on earth is good, then soldiers from more "civilized" cultures did best by killing and taking over the less-so. If you think your military opponents are doing more harm than would be done by opposing them, and that there are no less-harmful ways to get them to stop, then fighting is clearly the best option.
What are some possible implication of increasing/decreasing Israeli's millitary power?
Anything from world peace to total annihalition. Probably neither of those, but just a slight increase in length of conflict and slight increase in probability that Israel wins. Do keep in mind the possibility that you could WEAKEN the military by joining it (intentionally or un-), which may change the way this answer affects your decision.
Even if I conclude that Israel is a force for good (or for evil) in the world, am I likely to think so 20 (50) years from now?
Your beliefs in 20/50/200 years will differ greatly from your beliefs today. But today is the single best predictor you have. If you know what direction your beliefs will shift in, you should probably just apply the Aumann theorem to yourself and shift them now.
Should I expect a random EA who has done some ammount of (non-combatant) militry service to regret the actions she has done?
I don't recommend regret. Everyone makes mistakes, from believing falsehoods to failing to execute plans. I would remove the "non-combatant" proviso here, for two reasons - if you join the military, the chance that you'll see combat increases greatly. Whether you actually pull the trigger or only sign the paperwork for shipping goods to a base, you're enabling the combat.
Not sure if this is think kind of thing you're looking for, but just throwing some thoughts out there...
If the service is mandatory, why does it present a moral dilemma?
If you're in the military because you are required to be, it seems highly unlikely that that's where you would have ended up if you'd just done a broad search for where you can do the most good. So analyzing the utilitarian good of service seems like privileging the hypothesis.
It seems to me like you should think about it as a requirement that you need to get through, and that you should make the best of it while you're there. I'd think that the main way Utilitarian or EA thoughts would come into it is that you'd be thinking about how to best set up the rest of your career after military service to do the most good you can.
Thank you, but this is not relevant to my situation. I do have possible choices to make in which these dilemmas are an integral part.
Moved to your personal blog, since I mostly think that's more along the lines of what you intended. Let me know if you think differently.
Israeli here. It seems very unlikely that serving in the IDF is optimal in terms of global utility per marginal effort. On the other hand, using "tricks" to avoid military service might have negative costs in terms of subverting the rule of law and/or mutual trust in society (it is sort of defecting in Prisoner's Dilemma), but these costs are probably not so high (on the margin) as to offset the good you can do if you use this time for something truly effective.
If you are only thinking about sign of the effect, then, well. The morality of Israel's government is a mixed bag, but serving might produce some opportunities for you to influence for the better. It depends a lot on in which branch of the military you serve. For example, increasing technological capabilities might allow reducing civilian casualties during warfare, whereas serving as a combatant might allow you to directly reduce harm to civilians, although I imagine that in some situations that might call for disobeying orders at personal cost.
Btw, I also recommend you to visit the Israeli LessWrong meetups, where you can meet some likeminded people.
If you broaden the definition of military to include cyberwarfare in the vein of propaganda/fake news/hacking, then I think it is still a tremendously important activity. Military participation in on the ground activities - not as much. I'm personally of the view that actual ground activities now play the support role to cyber activities, rather than the other way around (Rather than try explain my views on that here, I'll just link you to the book I got that view from: War in 140 Characters: How Social Media is Reshaping Conflict in the Twenty-First Century).
I would like your assistance with gathering rational outside view so that I can make better moral decisions. The general context is that I consider myself an effective altruist with mostly Utilitarian ethics, and I have some more time of mandatory service in which I have considerably high degree of freedom to choose my path. The dillema is dependent on many questions, but my goal here is mostly to debias myself on questions relating to the moral stance of Israel or armies in general (although I care much more about the expected impact of my actions, irrespectively of whether it's done in the name of good or evil).
Hoping for a discussion, here are some questions I'd like to get an answer to, which are mainly here to give a broad sense of what I think might be relevant. Any helpful comments would be greatly appreciated, even epistimological tips to help me make better decisions on this topic would be of great help.