In spring 1861 the U.S. Army had roughly 115 medical officers and within months needed thousands. It filled the gap through governor-issued commissions, skipped examinations and contract hires, since a medical degree was not a prerequisite. William Hammond and Jonathan Letterman built an ambulance corps that cleared the Gettysburg wounded, but Hammond's request for a school was refused.
Exact numbers are uncertain, including the count of medical officers in 1861, the total of Civil War medical appointments, and how many volunteer surgeons held degrees. Whether ambulance-corps privates were armed is also unresolved.