Military service is service by an individual or group in an army or other militia, air forces, and naval forces, whether as a chosen job (volunteer) or as a result of an involuntary draft (conscription).
Few nations, such as Israel, require a specific amount of military service from every citizen, except for special cases, such as limitation determined by a military physical or religious belief. Most countries that use conscription systems only conscript men; a few countries also conscript women. For example, Norway, Sweden, North Korea, Israel, and Eritrea conscript both men and women. However, only Norway and Sweden have a gender-neutral conscription system, where men and women are conscripted and serve on equal formal terms.