[1] Edwin V. Sumner Jr. began his military career shortly after the outbreak of the American Civil War, when he was commissioned as a second lieutenant in the 1st U.S. Cavalry Regiment on August 5, 1861.

[1] He served as aide de camp to Major General George Stoneman between January 1863 and August 1863.

[1] He served as an Assistant Inspector General of the cavalry in the Department of West Virginia starting July 21, 1864.

[1] Sumner was mustered out of the volunteers and reverted to his Regular Army rank of captain on September 29, 1865.

[3] In 1890, he was elected a member of the Massachusetts Society of the Cincinnati by right of his collateral descent from Major Job Sumner, a veteran of the American Revolutionary War.