 Appointed a lieutenant colonel and assistant commissary general in 1861, Eaton was given the task of creating an effective supply system for the fledgling Union army.The large number of troops entering the Army at the beginning of the war was overloading the existing system.His work provisioning and distributing supplies to the troops led to President Abraham Lincoln's July 6, 1864, appointment of Eaton to the rank of brigadier general, U.S. Army, to rank from June 29, 1864.