Incredibly, in the 21st-century, roughly half of the world’s nation-states practice military conscription. According to Wikipedia, the countries on this list may still be enforcing military conscription.
In all cases, registration is required but military service may not be; this practice would certainly yield a number of draft refusers. In some cases, other forms of national service are compulsory which also generate principled refusal.
Starred * countries list provisions for alternative service or conscientious objection which exemption would also result in absolutist refusers; in some cases, the right to conscientious objection is constitutional. Failure by governments to provision conscientious objection or alternative service contravenes United Nation conventions, the Universal Declaration of Human Rights (Article 18) and the International Covenant on Civil and Political Rights (Article 18), to which almost all these nation-states are party.