Military service
With insufficient volunteers coming in by 1863, the Lincoln Administration was forced to begin drafting despite widespread complaints that it was unconstitutional and undermined states' rights (some states had conscripted men up to this point, but not the federal government). In July 1863, New York City erupted in the draft riots over the draft. However, anyone could get out by paying a $300 fee or hiring a substitute. Many conscripts and substitutes were criminals or men with debilitating health problems, and thus largely useless. The Confederate government had begun drafting men in early 1862.
Conscription was next used after the United States entered World War I in 1917. The first peacetime conscription came with the Selective Training and Service Act of 1940. When World War II ended, so did the draft. It was quickly reinstated with the Korean War and retained for the next 20 years, especially in the Vietnam War. Active conscription ("the draft") ended in 1973.
In 1979, President Jimmy Carter, a Democrat, brought back draft registration. All males up to the age of 26 are required to register with the Selective Service System, whose mission is "to provide manpower to the armed forces in an emergency" including a "Health Care Personnel Delivery System" and "to run an Alternative Service Program for men classified as conscientious objectors during a draft." No one has been prosecuted for violating the conscription law in the USA since 1986, but registration is required for certain benefits such as federal college aid, or in certain states, state college aid, or obtaining a driver's license. Women do not currently register for Selective Service in the United States; however they may still enlist for voluntary service. United States federal law also provides for the compulsory conscription of men between the ages of 17 and 45 and certain women for militia service pursuant to Article I, Section 8 of the United States Constitution and 10 U.S. Code § 246, however the federal governments utility of such militia conscripts is limited by the Constitution to repelling invasions and other service within the territory of the United States.

Countries with mandatory military service: 

Armenia: Armenia has compulsory military service for two years for males from 18 to 27 years old.

Austria: Austria has mandatory military service for all able bodied male citizens up to 35 years of age. Since 2006, the period of service has been six months. Conscientious objectors can join the civilian service (called Zivildienst) for nine months. A 10-month participation in the Austrian Holocaust Memorial Service, the Austrian Social Service, or the Austrian Peace Service is regarded as an equivalent to the civilian service.
Since 1 January 1998, females can join the military service voluntarily. The Austrian conscription referendum, 2013 resulted in the rejection of a proposal that would have ended conscription. Although the referendum was non-binding, both parties in government pledged to honour the results.

Azerbaijan: Azerbaijan has mandatory military service for all fit men, who are at least at the age of 18. Military service lasts for eighteen months for those without higher education, and for twelve months for those with higher education.

Belarus: Belarus has mandatory military service for all fit men from eighteen to twenty-seven years of age. Military service lasts for eighteen months for those without higher education, and for twelve months for those with higher education.

Brazil: Males in Brazil are required to serve 12 months of military service upon their 18th birthday. While de jure all males are required to serve, numerous exceptions mean military service is de facto limited mostly to volunteers, with an average of between 5 and 10% of those reporting for duty actually being inducted. Most often, the service is performed in military bases as close as possible to the person's home. The government does not usually require those planning to attend college or holding a permanent job to serve. There are also several other exceptions, including health reasons, for which one may not have to serve. Recruits accepted at a university may also choose to train under a program similar to the American ROTC, and satisfy their military requirement this way. Direct entrance to one of the military academies will also substitute for this requirement.

Myanmar: De jure the Burmese junta requires able-bodied persons aged 18 and over to register with local authorities. In 2011, civil servants, students, those serving prison terms, and those caring for an elderly parent were excluded from the draft, but they could be later called to serve. Totally exempt are members of religious orders, disabled persons, and married or divorced women with children. Those who fail to report for military service could be imprisoned for three years, and face fines. Those who deliberately inflict injury upon themselves to avoid conscription could be imprisoned for up to five years, as well as fined.
However, the conscription has never been activated under the military junta which ruled the country from 1988 to 2010. Myanmar's constitution states that male citizens over 18 could be called to serve in military, but it has not been activated either. As of 2013, Myanmar citizens are not required to serve in military.

Cyprus: Cyprus has compulsory military service for all Greek Cypriot men between the ages of seventeen and fifty. Additionally, from 2008 onwards, all men belonging to the religious groups of Armenians, Latins and Maronites, are no longer exempt, and also serve military service. Before 2016 military service lasted for twenty-four months. After that, former-soldiers are considered reservists and participate in military exercises and training for a few days every year. Conscientious objectors can either do thirty-three months' unarmed service in the army or thirty-eight months' community work In 2016, however, the Cypriot parliament had voted to reduce its mandatory service to 14 months and make up for lost manpower by hiring professional soldiers.

Denmark: As described in the Constitution of Denmark, § 81, Denmark has mandatory service for all able men. Normal service is four months, and is normally served by men in the age of eighteen to twenty-seven. Some special services will take longer. Danish men will typically receive a letter around the time of their 18th birthday, asking when their current education (if any) ends, and some time later, depending on when, they will receive a notice on when to attend to the draft office to be tested physically and psychologically. However, some may be deemed unfit for service and not be required to show up.
Even if a person is deemed fit, or partially fit for service, he may avoid having to serve if he draws a high enough number randomly. Persons who are deemed partly fit for service will however be placed lower than those who are deemed fit for service, and therefore have a very low chance of being drafted. Men deemed fit can be called upon for service until their 50th birthday in case of national crisis, regardless of whether normal conscription has been served. This right is very rarely exercised by Danish authorities.
Conscientious objectors can choose to instead serve six months in a non-military position, for example in Beredskabsstyrelsen (dealing with non-military disasters like fires, flood, pollution, etc.) or foreign aid work in a third world country.

Egypt: Egypt has a mandatory military service program for males between the ages of eighteen and thirty. Conscription is regularly postponed for students until the end of their studies, as long as they apply before they turn twenty-eight years of age. By the age of thirty, a male is considered unfit to join the army and pays a fine. Males with no brothers, or those supporting parents are exempted from the service. Former President Sadat added that any Egyptian who has dual nationality is exempted from military service and this is still in effect. Males serve for a period ranging from fourteen months to thirty-six months, depending on their education; high school drop-outs serve for thirty-six months. College graduates serve for lesser periods of time, depending on their education; college graduates with special skills are still conscripted yet at a different rank and at a different pay scale with the option of remaining with the service as a career. Some Egyptians evade conscription and travel overseas until they reach the age of thirty, at which point they are tried, pay a $580 fine (as of 2004), and are dishonorably discharged. Such an offense, legally considered an offense of "bad moral character", prevents the "unpatriotic" citizen from ever holding public office.

Finland: Finland has mandatory military service for men of a minimum duration of five and half months (165 days); depending on the assigned position: those trained as officers or NCOs serve for eleven and half months (347 days), specialist troops serve for eight and half (255 days) or eleven and half months, while rank and file serve for the minimum period. Unarmed service is also possible, and lasts eight and half months (270 days) or eleven and half (347 days). All males are required to participate in the drafting event (Finnish: kutsunnat) in their municipality of domicile in the year that they turn 18. The fitness for service and the actual induction to the service then takes place at the time and place decided individually for each conscript during the drafting event. The induction takes place usually at the age of 19 but the allowed age range is 18–29.