> especially if you have super strict civilian firearm laws like Costa Rica that make putting together defensive militias much, much harder.

Not refuting the larger point, but this part sounds questionable. For a country, rifles are easy to provision: just buy enough and keep them in well-guarded armories in strategic locations. Trained soldiers are much harder to come by.

South Korea has relatively strict gun laws and very few people own one at home. But almost every male goes through two years of military service. In case of a foreign invasion, it won't take 24 hours to summon millions of civilians, just throw each one a rifle, and there's your army.

But no one else has a standing army in this scenario so there is no such modern military that can conquer you before you can remilitarize. The moment one country starts militarizing in a world without militaries, you know their intentions and can start remilitarizing to counter.

But let's say Costa Rica had a standing army - are they going to stop that modern military from conquering them? Probably not, so why waste money on a half assed defense?

Germany, between WWI & WWII, officially has no military to worry about. Was able to create a Europe-conquering army very quickly.

So would you describe the Maginot line as a good investment?

Obviously not. Germany noticed lines have ends, and just went around.

So you're saying that a nation without a large standing army can build a new force well suited to exploiting weaknesses of its adversaries who spend substantially on maintaining investments in defense which contain those exploitable weaknesses?

One might go so far as to say that not having a strong standing army for an extended period of time actually proved militarily advantageous for the Germans in 1940 when their new army outmaneuvered an obsolete one.

I was responding to “The moment one country starts militarizing in a world without militaries, you know their intentions and can start remilitarizing to counter.” Lack of a military is quite a weakness to exploit.

The Brits abd French actually drastically cut military spending between WWI and WWII

Also, they went around it using, in large part, Czech armor they took when they invaded Sudetenland.

No, in this scenario someone made an army and conquered you, and now they own you and your resources.

> but what happens if nobody has a standing army?

The moment someone has a standing army, we are, by definition, no longer in a situation where nobody has a standing army.

If someone can magically instantaneously create an army, then Costa Rica should just do that the moment they're threatened.

The issue is that while someone is building an army, the rest of the world might stand by and do nothing in hopes that the army won't be used, via appeasement and negotiation, particularly if the world's culture is strongly set against having armies. At least until the aggressor starts conquering. That's how it tends to play out historically, so countries and kingdoms go to the trouble and expense of having standing armies, or being able to call them up quickly enough. Because there's always potentially someone who gains power that wants more, and plenty of people willing to follow.

> particularly if the world's culture is strongly set against having armies.

If the world's culture is strongly set against having armies, and one country effectively threatens them by breaking that taboo, then I would at least expect the world to instantly cease all trade and transport links with the arming country.

That may not be enough on its own to force the taboo-breaking country to disarm, but I don't see any contradiction in a world culture which is against having armies while also ruthlessly dedicated to temporarily re-arming and exterminating the first country that breaks the taboo.

There are hard coordination and rule of law / presumption of innocence questions to solve there, but I don't think we can necessarily assume that this world culture will stand idly by while their enemy works to undo the very thing that defines the culture.