By January 1863 it was clear that state governors in the north could not raise enough troops for the Union Army. On 3rd March, the federal government passed the Enrollment Act. This was the first example of conscription or compulsory military service in United States history. The decision to allow men to avoid the draft by paying $300 to hire a substitute, resulted in the accusation that this was a rich man's war and a poor man's fight.

The Enrollment Act resulted in Draft Riots in several American cities. There was heavy loss of life in Detroit but the worst rioting took place in New York City in July. The mob set fire to an African American church and orphanage, and attacked the office of the New York Tribune. Started by Irish immigrants, the main victims were African Americans and activists in the anti-slavery movement. The Union Army were sent in and had to open fire on the rioters in order to gain control of the city. By the time the riot was over, nearly a 1,000 people had been killed or wounded.

It is estimated that of those who took part in the American Civil War, 75,215 were regulars, 1,933,779 were volunteers and 46,347 were drafted and 73,600 were substitutes. Officially, 201,397 men deserted, of these 76,526 were arrested and returned to their regiments.