Our concept of drafting men for military service should be viewed against a long, inherited, Anglo-Saxon-based tradition of militia--essentially the able-bodied males of a certain age-range, who could be called to arms (generally those held by the individual) by a ruler or other authority. (In the Scottish clan tradition, failure to respond to the call could result in execution or, at the least, shunning.) Among the colonies and the United States, a distinction was made between the organized militia (who mustered periodically) and other males, generally over or under the ages prescribed for the organized militia. (Today, the National Guard embodies much of the former militia concept, but is voluntary and open to females as well as males.)
In time of (delared?) war or emergency, the organized militia could be "called up," or mobilized by the governor or President. (Individuals who couldn't wait could volunteer by enlisting in the regular military, or--for example, in the Civil War and War with Spain--as members of volunteer units, part of the provisional augmentation of the armed forces.)
I have always thought of conscription, or draft, as the "calling up" of men who were neither involved in the organized militia nor part of the volunteer or regular service units--in other words, harking back to the tradition that every male in the age-group or conditions specified for that era was subject to mobilization. If I am correct, exemptions were always an anomaly--service was an obligation of citizenship, and avoiding or running away from participation was the exception, historically, and ealt with differently under different circumstances. (The inclusion or formal involvement of females is, of course, an additional, modern consideration.)
As you worded your approach, I sensed a different perspective, and throw this out for your additional consideration.
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