He mustered and served as colonel in the 6th Pennsylvania Cavalry Regiment (known as Rush's Lancers) from October 1861 to September 1862.

Both his maternal and paternal grandfathers, Benjamin Rush and Richard Stockton, were signers of the United States Declaration of Independence.

[5] The regiment entered Virginia on March 10, 1862, and was attached to the Second Brigade, Cavalry Reserve led by William H.

[8] The regiment fought well at the Battle of Hanover Court House, capturing prisoners and serving as scouts and couriers.

[7][12] He took sick leave from the regiment on April 25, 1863, due to a relapse of malaria contracted during the Mexican-American War.

[6] He helped organize the Veteran Reserve Corps and served at Rock Island Prison from November 10 – December, 20 1863.