At the time of the American Civil War, with two million men under arms, a US Army that in pre-war days had depended upon a minute number of technical troops now required virtually an army of specialists alone. Special sharpshooters were recruited for skirmishing duty; men whose wounds would have led to their discharge in the past now found themselves guarding important posts in the Veteran Reserve Corps; and large numbers of civilians found themselves in uniform as members of the Telegraph or Hospital Corps.

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