This article writes about more than 20 countries that don't have militaries.
That's interesting. But it is a simplistic exercise based on a CIA list of countries without formal "militaries."
Actually, if you define a "military" is one capable of fighting conventional combat against other regular militaries, most countries don't have militaries.
Most "militaries" are simply capable of beating down unarmed civilians. So at best they are riot police.
Writing about those nations would be an interesting article.