| Country | Military service age and obligation |
| Italy | 18-27 year of age for voluntary military service; conscription abolished January 2005; women may serve in any military branch; 10-month service obligation, with a reserve obligation to age 45 (Army and Air Force) or 39 (Navy) (2006) |
| Jamaica | 18 years of age for voluntary military service; younger recruits may be conscripted with parental consent (2001) |
| Jan Mayen | void |
| Japan | 18 years of age for voluntary military service; Maritime Self-Defense Force mandatory retirement at age 54 (2011) |
| Jersey | void |
| Jordan | 17 years of age for voluntary military service; conscription for males at age 18 was suspended in 1999, but reinstated in July 2007 in order to provide youth training necessary for job market needs; all males under age 37 are required to register; women not subject to conscription, but can volunteer to serve in non-combat military positions in the Royal Jordanian Arab Army Women's Corps (2010) |
| Kazakhstan | 18 years of age for compulsory military service; conscript service obligation - 2 years; minimum age for volunteers NA (2004) |
| Kenya | 18-26 years of age for male and female voluntary service (under 18 with parental consent), with a 9-year obligation (7 years for Kenyan Navy); applicants must be Kenyan citizens and provide a national identity card (obtained at age 18) and a school-leaving certificate; women serve under the same terms and conditions as men; mandatory retirement at age 55 (2011) |
| Kiribati | void |
| Korea, North | 17 years of age (2004) |
| Korea, South | 20-30 years of age for compulsory military service, with middle school education required; conscript service obligation - 21 months (Army, Marines), 23 months (Navy), 24 months (Air Force); 18-26 years of age for voluntary military service; women, in service since 1950, admitted to 7 service branches, including infantry, but excluded from artillery, armor, anti-air, and chaplaincy corps; HIV-positive individuals are exempt from military service (2011) |
| Kosovo | void |
| Kuwait | 18-30 years of age for compulsory and 18-25 years of age for voluntary military service; women age 18-30 may be subject to compulsory military service; conscription suspended in 2001 (2009) |
| Kyrgyzstan | 18-27 years of age for compulsory male military service in the armed forces or Interior Ministry; service obligation - 1 year, with optional fee-based 3-year service in the callup mobilization reserve; women may volunteer at age 19; 16-17 years of age for military cadets, who cannot take part in military operations (2011) |