Conscription, also known as the draft, is the state-mandated enlistment of people in a national service, mainly military service. It has existed since ancient times, but there have been few instances of universal conscription, which calls all those physically capable between certain ages. The usual form, even during total war, has been selective service. Conscription is controversial for a range of reasons, including conscientious objection to military engagements on religious or philosophical grounds, political objection, sexism, and ideological objection.

During the First World War, the UK government saw no alternative but to increase numbers by conscription, which was compulsory active service. In the United States, conscription had been applied during the Civil War by both North and South, but it was primarily effective as a stimulus for volunteering and was abandoned when the war was over, not to be revived until World War I. As of 2023, many states no longer conscript their citizens, relying instead upon professional militaries with volunteers. However, many states that have abolished conscription still reserve the power to resume conscription during wartime or times of crisis.

In Finland, conscription is part of a general compulsion for national military service for all adult males. The ability to rely on professional militaries with volunteers presupposes some degree of predictability with regard to both war-fighting requirements and the scope of hostilities.

Overall, conscription is a controversial topic that has been used throughout history to increase the number of people in a countrys armed forces.