All the Great Powers adopted peacetime conscription by the end of the the 19th century, except Great Britain and the United States. As weapons became more technical and armies could not cope with the young men of growing populations, conscription became less useful. Compulsory education replaced military service. The advent of military aircraft posed a threat to the general population so industrial resources were mobilised on a forced basis, together with human resources.
In World War I the Great Powers fought with conscripted military forces. Until 1916 Great Britain depended on volunteers, then resorted to use conscripts. The United States enacted the Selective Service Act of 1917 upon entering the war. Canada relied on volunteers until 1918, when it used conscripts.
Although prohibited by the Versailles treaty from conscripting troops, Germany reintroduced the system in May 1935.
After the war all the Great Powers except Great Britain and the United States continued universal military service.