[1] The first peacetime conscription in American history was authorized under the Selective Training and Service Act of 1940 in September 1940.
This was well in advance of the country's actual entry into World War II, but in clear anticipation of the likelihood of involvement.
Unlike the earlier registrations, its purpose was indirect; the individuals were not actually liable for military service.
This registration was essentially a very broad inventory of manpower and skills useful to the war effort, potentially bringing under-utilized or unemployed men back into a more fruitful occupation, and allowing for the release of easily replaceable, younger, or more fit men to fight.
The back of the card included a physical description of the registrant, with race, height, weight, complexion, "other obvious physical characteristics that will aid in identification," and a certification that the registrant and registrar attested that the answers given on the card were true.